Is it possible to find a 1 ghz phone for under $100?

1GHz? Which carrier? On or off contract? New or used?

There's a few used phones with a 1GHz processor for under $100 or maybe a little higher. You got the Droid 2, Droid X, Droid incredible...just to name a few. Those are all Verizon phones though.

 

Pre-Paid and 1GHz? Well thaty's going to be very tricky if not impossible.

T-Mobile has the Samsung Exhibit II 4G for $198 if you get it from Amazon (the Pre-Paid version is cheapest)

There's a $154 Motorola Bravo with a 800 MHz Proc on Amazon.

I'm also looking for cheap but good phones for the prepaid pay as you go. You'd have more options if you were willing to raise your budget to $250.
Take a look at my thread in my search for a under $250 (or close to that) budget Android phone. Someone may come upon something nice and cheap.
http://androidforums.com/android-lounge/531143-best-budget-unlocked-t-mobile-phone.html#post4220510

 

Droid Bionic.

 

Isn't the Bionic a Verizon only phone? OP stated they are on T-Mobile

 

My mistake I only read the first post.

 

With due dilligence you should be able to nab a nexus one for about $100.

 

I have seen exhibit II 4g's on ebay that have gone for under $150. That's about it though. You can hop on ebay right now and get a G2 for ~$130 or so, but it's only 800 mhz but benchmarks as well as some 1 ghz phones.

MSM7x30 (MSM7230 MSM7630), MSM8x55 (MSM8255 MSM8655) and QSD8x50A (QSD8250A QSD8650A) are Qualcomm's 2nd gen Snapdragon processors. How fast are they? - Smartphone Benchmarks (SmartBench 2010/Quadrant) Forum

 

Yes you can. You can also use any unlocked phone as well. So basically any T-mo locked phone or any unlocked GSM phone. And you can use it on any plan whether it is post paid or prepaid.