Hi, if you read my other postings about this topic, you'll see that I am generally a proponent of home ownership, UNDER THE RIGHT CIRCUMSTANCES. You need to make a very educated decision about buying a house. 90k sounds like it is in the ballpark of what you can afford with rents as you quote them, but there are a few things to watch out for:
1. It doesn't seem like you are including property taxes in you monthly payment (you don't pay them monthly, but they must be included in your monthly payment in order to make a fair comparison)
2. Are you sure you can get a mortgage? You quoted your car loan at 13%. That's outrageous, and the only reason that I would guess that you got stuck with such a $hitty car loan is because you have pretty bad credit. Home lenders won't touch you with a 10 foot pole nowadays, if that is the case.
3. The previous poster's comment about "They couldn't have built that house for 90k" demonstrates my third point. Yes they can.....if it is of below average construction quality (regardless of the fact that the housing market in FL took a huge dump.) Home builders are by no means created equal, and I've seen lots of people buy new, thinking, "Great, if I buy new, I will have no maintenence issues," and be sadly mistaken. The builder will throw in a warranty, but that involves the builder sending his people to take care of the problems (and you WILL have problems, unless you are dealing with a top-notch builder, but those builders don't build 90k houses, even in this market) which will waste your time (for me, my time is WAY more valuable than my money, and I can't wait around all day for the builder's A/C guy to show up, like my mother did a few weeks ago, and she bought a house from a middle-of-the-road to better quality builder.)
But, to answer your original question, borrowing "from Peter to pay Paul" won't influence your creditworthiness at all. It does make sense to take out the extra Stafford loans to pay off high-rate debt, but doing so won't improve your creditworthiness.