I am planning on putting 28,000 USD into repairs. 

We don’t feel as though these properties would work for fix and flip investors mainly because of the area but we are thinking of negotiating seller finance and putting about 3k into repairs and using them as rentals.

A couple months ago I was looking at a triplex that came up for sale in a close suburb,   long story short despite suffering from long term poor management, needing substantial exterior repairs, and having damage and 2 vacant and gutted units left over from tenants-from-hell it ended up selling to somebody else for 30% over asking,  needing another 20% of the asking price (at least) in repairs.  

Can I go after that roofer for repair?

That is their estimate of what it would cost to rebuild with the same kind and quality. 

They can afford the monthly payments but don't have the downpayment for the house saved yet- they have a plan to do so in the next year.We offered to allow them to rent at a lesser rate for a year (to help them save for the house) and they be responsible for small repairs and at their lease renewal we touch base and see if they want to buy.

If you do all the repairs at once, city hall might require more costly repairs than you expected.

If have you some or all of these things you could send copies with the check and letter explaining repairs.

With old houses, things break fairly regularly so if you don't have a good local team to fix things, you will either frequently overpay for repairs or get bare minimum fixes that don't last very long. 

I highly doubt that you will be able to create $25,000 of equity with $1,000 worth of repairs (which seems a bit low anyway)  Other than that it doesn't look bad but it all depends on the area.