Looking for an app for rental properties.

I own 2 small trailer parks and a few other duplexes etc. in total around 40 units. I’d like to get an app to see charts and graphs and to also document repairs that I do etc. I keep looking at different ones but my big concern is 80% of these people pay cash so I’m not sure if it’s really worth it. Right now I use an excel spreadsheet to document rent before we deposit. It would be cool to have something that i can take pictures of receipts and upload to each unit. Any ideas?