@Dan H.. I use a smaller Capex number than is generally advocated here. Here's why. I have 10 SFR's, mostly 1100 square feet or less. I do my own maintenance and repairs, so that's an immediate large cost savings. 4 of my houses have vinyl siding, so there is no painting in the future. 2 of them have window units, so no big AC repairs. I can handle any repair not involving Freon. A water heater? Usually lasts about 10 years, cost 450 bucks for a capex of $3.75 a month when installing it myself. New roofs? Where I live we get hailstorms about every 5-10 years. Last storm we got 2 new roofs paid by insurance and the installer rebated me 500 bucks per house, in cash. Early on in our rental business I had to call a plumber to snake a drain. almost 500 bucks. I bought a power drain auger for 380 dollars and have used it twice and will never pay that 500 bucks again.
Every landlords situation is different. I do have a reserve fund of about 30k and we put 1k a month into this fund for repairs and maintenance and capex and we feel comfortable with that.