In one of my properties there are plenty of oil stains and cracks in the concrete and I would like to redo it so it looks presentable to tenants again.I've seen some repaint there garage and some do an epoxy coating.

Without knowing much about your local area, the exterior condition and MEP systems in the house I'll make the following suggestions so take with a grain of salt ;) First, I'd wash those walls and repaint most of the rooms a clean white or something neutral.

Full repaint, brand new LVP flooring and carpet throughout the home.

I expect to get the amount from the reserve later.)The 38k income in 2017 is not completely representative, because some repairs were delayed (as is often the case with long serving tenants making repaint, kitchen resurface etc. difficult to do).

Current cabinets will be repainted and the backsplash will be cleaned up a bit.

Remove the rotted boards, sand entire front porch to remove layers of paint and repaint?

I have had to repaint and refloor entire homes to eliminate that smell. 

Assuming it doesn't need any major work (I would get any home I purchased inspected, of course), it needs at the very least to be completely repainted, the exterior needs to be freshened up with new paint, and it could use new appliances in the kitchen.

Kitchen could probably use some sprucing up - repainting cabinets, new hardware, new appliances.I saw a similar post on here where someone did a similar amount of work for ~15k, though her prices were competitive.

The best way to help her is probably to put in a little sweat equity doing some repainting, etc.