I am looking at buying a used Acrosonic for my 5 year old to start lessons. The seller says a few of the keys stick. Is it worth trying to get this repaired? The price is only $75.00 which seems like a steal! If I get this repaired, will it raise it's resale value in the future?

Have a technician give it a once over. The keys could be sticking because they need to be eased, or the hammer shanks have warped and the hammers are rubbing, or the lost motion is out of control, or a mouse lived in the piano and chewed it up, or, or, or, or......

If a tech gives it a green light then it's up to your budget and sound sensibilities. IMO taller is better-all mechanical function being equal.

You get what you pay for. If in good shape, this is a $800-$1200 piano. The price is way too low, and sends up red flags that the piano needs expensive repair. Do not buy this without approval by a technician first.

Sticky keys are insignificant in the overall scheme of things when evaluating a piano. Your priorities should be whether the big things are in good shape i.e. the soundboard, pinblock, bridges. After that I'd check out the condition of the strings and the action.

Don't just assume that the piano will be fine. I've seen too many people purchase a piano that looks wonderful only to have it tuned later and find out that it's a POS. Hire a tech to evaluate it BEFORE you buy it. You'll save yourself a lot of grief in the long run.