@Andrew Kerr made some great points and I've (sorry, Andrew) stolen his thoughts around CAPEX, maintenance, etc. for other folks in a similar boat. When rubber meets the road, these low-cost/low-rent properties only make sense if you're turning and burning them, or are adding them to an existing portfolio where you have sufficient reserves already.
I've got a property I am looking at that rents @ ~1750 for 2 units, so taking 10% for CAPEX -- which is an estimate on my part, good, bad, or indifferent -- sets aside $2,100 per year just for CAPEX. Is this a good number? Don't know. If I need to replace the roof on this property, chances are I'll need 2-3 years of that CAPEX number set aside to do so.
If you're only socking away 10% of 500 rent, that is $600 a year. I think most properties you want to sock away a few thousand dollars, at least, to have a reserves account. Then you pay back the reserves account with the CAPEX "expense" you've (hopefully) set aside properly.
$20 says the roof on my property will probably cost the same as yours. So assume $5,000 for a new roof. Setting aside $600 per year means you'll need to go 8+ years without a single CAPEX expense to have the reserves ready for that $5,000 roof. Is that likely? Probably not. My last property in 2 years I had to call a plumber twice, a heating/AC technician once, and my handyman 3 times. Bad management on my part, perhaps, but nonetheless the problems do come up.