Yes, of course there are concerns, but there are in the other alternatives too. The main ones if you are having the work done from afar is quality control and the speed of which the work gets done. There is no way around it, you have to have someone intelligent and reliable in charge and such people cost more then the grunt labor.
In one of my parks I have my manager’s husband running a crew and it has worked out pretty well, though it seem to take a lot longer then it did when I was running a crew reshaping my apartments.
In another park I hire a young guy who has his own crew to do the work. He does very good work but it is a bit on the pricey side.
Both systems are working well for me for now. One alternative I will no longer do is the handyman special. Rather then selling off an old home for $1k or so to some guy who never seems to get around to the handyman part, I would rather pay to put the home in good ship shape and just sell it for my costs if need be.
Just about all older homes have soft floors (at least mine do.) It’s no big deal. Of course day one is always the tear out. Once the old flooring is removed it is pretty quick work to take a circular saw set to the depth of the flooring, to cut out the bad areas. One thing I have my guys do, that not everyone does is to cut some 2x4s and run them between the floor joists so that wherever two pieces of plywood join in the patching, the edges are supported from underneath. It just takes a minute to do and makes the area feel really solid.
I wish I could say 2000 homes are old.