About to get my first deal

[Quinterrius Eatmon]

So I'm pretty close to getting my first property under contract. With that being said, I just want to make sure my offer make sense, the last think I want to do is blow the deal by low balling. So I have done some research as far as the TAV and the FMV around 35k. Now, when I looked at comps in the area that sold recently, they where closer to the 40+ range (none were rehabbed). It's a 2 bed 1 bath 950 sqft single family home. It needs work inside and out but I'm sure someone could make a profit off a very basic flip (I would rent it out in my opinion). I think the roof also may need a little work done the owner said it was put on in 2005 after hurricane Katrina. I estimate the repair cost is between 10-18k depending how the buyer wants to go about the renovation. So I put the formula together for my offer I'm just a little worried it's REALLY REALLY low. The offer I have come to is 3-5k. Is this a fair offer or am I really low balling the seller?