Exciting times ahead for you. 

i suggest @J Scott's book on estimating repairs. 

The home is listed for $12,500 but it needs major repairs.

I would probably estimate vacancy at 8-10% to be safe as well as raising your CAPX and repairs to 7%. 

Yep, fire damaged properties Always have more in repairs than you think unless you’ve done at least a few of them.

from buying a home in need of repair so I can rehabilitate it and sell it. 

The owner estimated the costs, utilities, maintenance, and repairs to be approximately $35k per year as he pays all the utilities for the tenants.

I’ve talked to lenders, real estate agents, I’ve ran numbers on over 50 deals, I’ve came up with 4 different scenarios on 20 of those deals with different numbers on rent, rehab, repairs, escape plans, etc.

I find myself "googling" for every repair that comes up even though many of the jobs are small and could be completed fairly easily by a "jack of all trades" type (or me if I had more time!). 

If the 10% would dig into your returns more than you're comfortable with, go ahead and manage yourself to get the experience, but have the knowledge that this property may always be one that requires your direct attention.