You should look at having 2 or 3 batteries if you plan on a rental business. That way you can charge the batteries slower and change when they are about 80% discharged. You will get many more (hundreds more) recharges from you batteries. Higher outlay but more cost effective in the long run.
A Li-ion cell used between 30% and 90% charge will give you several thousand recharges.
A Li-ion cell used between 0% and 100% charge will give you 500 - 600 recharges
This is the principle behind Tesla Power Wall. It uses Panasonic 18650 cells that have a life of 500 cycles yet they give expected life of the Tesla Power Wall 10 years with daily cycling.