This was common wisdom back when houses weren't insulated and walls, doors and windows were drafty and porous to humidity changes. If your house is modern or updated to code there should be no problem with placing a piano on an outside wall. There are a few factors to watch out for when placing a piano - avoid direct sunlight as much as possible as UV light will fade color from a finish over time, and fluctuations in heat will affect the tuning somewhat - though not as much as humidity changes will. Also avoid places with moving air such as heat registers and proximity to outside doors - especially if they tend to get left open during warm weather. Another thing to watch for is fireplaces or woodstoves used as a heat source - try to keep pianos as far away from direct heat or blowing air as possible. If there's no other option than to place a piano in a non-optimal position there are products such as covers to protect from UV or piano specific humidity systems to help stabillize the tuning. Feel free to call and ask about price and availability...
Many parents start their kids on an electric piano or inexpensive keyboard thinking if they like playing piano they'll buy something later. Teachers have varying opinions about this - it can make sense for very young beginners as it's more about the teacher relationship and exposure to general musical ideas than actually playing piano. The problem starts when they do become interested and compare the teachers piano to their own practice instrument. Learning to love music is really learning to like practicing and the more inspiring the instrument the more likely they will enjoy practicing. Keyboards are viable instruments and some are quite amazing and useful for what they do, and there are situations that make sense to own one such as needing to play with headphones or moving frequently - or playing in a band, but keyboards will never replace fine acoustic pianos - just like electric guitars will never replace acoustic guitars - they're different instruments with a different playing experience, both tactile and aural. You will rarely, if ever, see a fine classical pianist playing a concert on anything but a fine acoustic (large grand) piano. That's because they need fine gradations of tone and touch only obtainable on a quality acoustic instrument.
This is a tricky question - the standard answer is once or twice a year depending on how picky you are. Once a year is always adequate to compensate for seasonal changes in humidity and if it's tuned at approximately the same time every year it will remain at a consistent pitch. Tunings do fluctuate with varying humidity as the soundboard shrinks and swells, which in itself may not be noticeable unless the unisons (more than one string on the same note) drift also. So more than once a year can keep the unisons better in tune throughout the seasonal humidity changes. Letting the piano go for more than a couple years may result in loss of pitch - the whole piano may go flat - which may necessitate an extra pitch adjustment - which is a rough tuning to get the pitch close enough to do a finer tuning. The problem with having to do a rough pitch adjustment is it compromises tuning stability because the more you move the tuning pins and stretch the strings, the less predictable the long term stability will be and the piano will almost certainly go out of tune sooner than if it were regularly tuned.
That being said, I'll sometimes recommend tuning at less frequent intervals than once a year. If the piano is older than 50 years or so, or a very small piano, often those instruments are not as receptive to fine tuning and will always sound a little off - even the unisons - due to older strings or just an overly compromised scale design. Older and smaller pianos are also generally less responsive to humidity changes and don't tend to change tuning as much with humidity fluctuations, so even though they don't tune up as well to begin with, they can be more stable.
If it's a newer piano, ie. less than 50 years old, and well maintained it could be worth close to what you payed for it as pianos don't tend to depreciate as much as less durable goods. The exception may be smaller grands and uprights as they tend to be less quality in their design and construction. If it's a fairly nice piano in good condition you may be able to find comparable instruments on Ebay or for sale by online retailers. Be aware that whatever price is listed is more than they expect to get as most people try to negotiate a lower sale price - sometimes as much as 30-50%. The actual sale price will vary by region as well - more in a large market, less in a smaller area (like Eugene).
Older pianos are much more dependent on the actual condition and should probably be evaluated by a technician. There is no official piano blue book pricing for older pianos and you pretty much need to rely on the opinion of the local technician who hopefully has lots of experience with the local market. Of course you can always ask for what you want price wise - you may get lucky - but it's also good to have a realistic idea of what's normal for your area.
Pianos built before 1900 should be especially suspect as to condition - unless they've been rebuilt by a competent professional they need all new strings and action felts at the very least and other rebuilding work is usually required for best results adding up to many thousands of dollars investment. Without this work an older piano is not capable of playing consistently with enough subtlety of touch and tone to be considered musical in nature. Pianos from this era are also likely to be an earlier or pre-modern design - especially before 1880 - and may never reach the performance level of a more modern piano. Most pianos have a stamped or inked serial number around the area of the tuning pins that can be cross referenced with the Pierce Piano Atlas which most serious techs should own. There are a few websites that offer to date pianos given the name and serial number - some charge a fee - this one seems good and was free at the time I looked : http://www.pianotuningmelbourne.com.au/piano-age/ They may not have all of the older manufacturers in their database but it's worth a try.
Moving a piano in itself shouldn't make it go out of tune, provided it gets tuned regularly by a competent tuner. In other words the vibration to the the piano caused by moving shouldn't affect a well tuned (ie. stable) instrument. However there may be an environmental effect of differences in temperature and humidity during the move and at the receiving end that are significant enough to affect the pitch or the unisons or both. If a piano is moved within it's local environment to a room with similar temperature and humidity in a brief period of time (1-2 hours) and isn't overly stressed during the process it shouldn't need extra tunings other than its regular 6 - 12 month period. Of course you need to use your ears to determine if it sounds out of tune, and for many pianos that don't get tuned regularly moving is a great excuse for getting back on track. I usually recommend a couple week acclimation period before tuning after a move - not because it actually takes that long to reacclimate to a new environment (it really only takes a few hours) - it just seems like a good amount of time for everybody to settle in and get used to a new environment, and occasionally there are extenuating factors which aren't accounted for like a piano being stored in a garage with extreme humidty (or lack) - or moving from a coastal environment or other extreme which can take more time.
RPT ia a classification given by the Piano Technicians Guild or PTG (got to PTG.org to find out more). An RPT has passed a series of tests at at least a minimum competency level for proficiency in aural tuning, action repair and regulation and various other issues like string splicing and replacement and lyre adjustment and repair. These tests are fairly rigorous and require at least a couple years of focused study and experience to pass. Not all professional technicians choose to take these tests - even some members of the guild, and not having the RPT designation does not necessarily infer lack of experience or skill. Guild members have an Associate designation until they pass the tests.
PTG members are encouraged to become certified as RPTs in order to ensure that members are providing competent service with a basic knowledge of the depth and breadth of the field of piano technology. Members are also obliged to follow a set of professional and moral codes of conduct laid out in the bylaws. As a professional piano tech I consider the yearly fee to be well worth the value I get from information, extra training, and the peace of mind it gives my more informed clients that I consider myself a skilled professional and act accordingly.
I've been asked this a surprising amount over the years - of course I come to the piano to tune. I can also do many repairs, cleaning, regulation (wholesale action adjustment) and voicing hammer felts or tone regulation at the piano. The types of work I do where I would need to move the piano to the shop are more like refinishing, replacing all the strings, major action rebuilds, structural case repairs etc...