Can i start a new cell phone account with a smart (android) phone off Ebay on a network like Tmobile or Sprint?

the simple answer to your question is no. you would still have to sign up for 2 years, and get a data plan. that's why most people just get the phone from the provider. it's as cheap or cheaper than buying one off of ebay or ??. the only way this might work out for you is if you get the phone for free from someone else who is upgrading or getting rid of their phone. and they don't do pay as you go right out of the gate. you have to do your 24 months just like the rest of us.