Good Deal, Great Deal, or 50/50

[Brett Wells]

my name is Brett I am still new but have a great mentor to follow.  He owns a demolition company and had this deal come to him that needed to be demolished.  Location is in Boise,id 950sqft 2bed 1 bath home with a half acre lot valued at $150,000 it is being purchased for $120,000.  I offered 100,000 which includes my $20,000 budget to fix and rent it.  The demo man is lending me the 100,000 at 5% with a 5 year payoff.  KICKER there is a mother in laws house behind the main house that can be turned into a rental as well has electricity, needs plumbing potential 1 bed 1 bath.  As well lot has room to add a future smaller home.  I think I am going to do the deal, need a 2nd opinion I did the calculator but not sure if i calculated it right with having a 20,000 budget.

Thanks