Good deal ?

Hey guys,

I'm here to asking some help.
I just arrived in Miami since 2 months and I'm here for 18 months.
With my wife we search a car to buy.

A colleague is selling his Acura TSX 2006 with 105k miles, excellent condition.
The price is below what I saw on www.kbb.com (he selling his car at $7500).

An another colleague selling a 2008 Scion with 69k miles, manual, rebuilt title in good condition at $4800.

I don't know enough about the car market and am a rookie. First car in the US...

So, my questions are :
- If we want to sell it back in 18 months, maybe one of the two deal are a best one, or not ?
- How I can know if it's a good deal ?
- 100k + miles is not too much ?
- Any advice, I'm lost.

Thanks for your help.