I got a used Trek off of Craigslist for a price I'm happy with. 29" seems to offer better performance than the 26". But I went with the 26" tires because its a more common size. (Shtf, don't judge me, lol)
I read alot of articles like this to decide the appropriate frame size:
http://m.bicycling.com/maintenance/bike-fit/if-bike-fits-buy-it
I'm new to biking, so these are newbie opinions.
This, buy a used, name brand bike, CL is a great place to shop for them. The residual value of bikes is terrible, which is good if you are buying used. Patience is key...