Why would you need to get a loan if you have 15 mortgage free properties? Just for argument sake, if you are renting them out for $750 you should be cash flowing $400/mo minumum on them. If just 10/15 are rented then you should bring in 4,000 a month. Wait 3 months and pocket 12K and finance your own repairs. Man I would love to have 15 properties free and clear. My goal was always 10 by 30, 40 by 50. I have 5 right now, but only 2 years till the 30 mark so I'm not sure if I'm going to make this deadline!
If you have to get a loan it won't be a problem at all regardless of credit. You have equity and thats all you need.