Triplex. First time investor. Wanting opinions on first deal.

[Mason Anderson]

I am diving into the real estate field. Taking over my Gmas Triplex. I have looked at doing this many ways and think I have found the best option. Let me know if you agree or disagree... please. This is my first deal and would love all the help I can get. 

Triplex in a pretty decent area close to town. My Gma owns the property and owes nothing. Was hoping to take it over on contract. Have her give me the title for a small down payment. Then pay her $400-$450 monthly for 8 years and maybe 6 months depending on appraisal. Needs a ton of work, but I am hoping it appraises for as low as possible. Thinking $40,000. I have the money to do rehab, hopefully $10,000-$12,000. Also want to add SQFT by enclosing the porch and adding another bedroom to the front apartment (would this be worth the money it would take to do it?). Hopefully after all that the new appraisal comes back at around $68,000-$75,000. I have 3 pretty strong comps supporting that. Then looking to take 75% equity out and find another deal. Would rent the plex out and cashflow for around $600-900. My total investment would be the small down payment ($1,000-$2,500) and the rehab ($10,000-$12,000 with porch addition and bedroom $15,000). 

Any tips or opinions?