My first possible deal

[Edward C.]

Hi, I'm Just starting, looking forward to my first deal.
The owner has the home through probate, there is a 20K medical lien and he owes about 2K in current and back taxes. He is not able to afford to pay the taxes and the home is in much disrepair. The ARV for this home (1344sq ft, 6rm, 3br, 1 bath) has a comp of 130K.
It needs a lot of work of about 90K but when the work is done it will have another 600 sq ft (walk up attic space), 3br and 1.5 bath. Similar homes like this comp at 190K.
190k minus the 90K work to go in to it, I'm left with 100K for Lien, Tax, holding, closing, and such (65K costs, roughly). This would give me 35K profit assuming I can sell it for the 190K, and I'm not even convinced I can get that.
I'm thinking of offering him a small 5K up front for the home, and 20% of any profit at the end, to lower the upfront cost as much as possible.
I'm trying to keep myself from losing my shirt by keeping the largest margin of error possible so I can't see offering him more upfront. On negotiation, if he does not except this offer should I consider upping his back end % to say 30 or 40%?

Thank you in advance for any advice you may offer.

Sincerely

Ted Cole