Can I get an iPhone for tmobile?

I have had tmobile for years and I really want an iPhone. I don't really care anymore if it's the 3GS, the 4, or the 4s. (although I would LOVE the 4s). I'm NOT going to buy an unlocked iPhone because it's so much more expensive. Where could I get an iPhone to unlock and jailbreak it myself for sorta cheap? Maybe eBay or amazon?

Craigslist you can get iphones cheap.
but the iphone 4 can only be unlocked for tmobile if on 1.59.00 baseband.
and the 4s can't be unlocked, unless bought that way.

EBay and Amazon as you said should be your best options but as far as unlocking it it depends on if there's one at this time. You may have to further by a Gevey SIM in order to unlock should a software unlock not be possible

Just buy at&t iphone and get it unlocked at appleunlockcodes.com for $60 this is a factory unlock which is permanent. No jailbreak needed.

You can get a network locked iPhone for low cost from Ebay.com.
You can Jailbreak your iPhone. You can get the jailbreaking guide from www.guidemyjailbreak.com.
You can unlock your iPhone through remote unlocking method. You can get the remote unlocking for your iPhone from http://www.wickedunlock.com/ this method of unlocking is safe, simple and affordable.
All the best mate.