Most companies when they buy a UPS they will run it until the batteries fail due to age. Often certain models of UPS (APC) over charge the batteries and kill them in 18 months. This forces you to call the manufacturer and ask for new batteries for which they charge a preimium.
What normally happens is that the UPS is then tossed out.
I think there is a business for someone to get these UPSs workinig, supply compatible batteries and do the installation for the customer.
For us when we sell UPS we normally have to scramble and go and buy "fresh" batteries as they are not the kind of things that you should store them. This means that we have to go out and pay premium rates for the batteries locally.
Selling refurb UPSs.
Firstly there is a constant flow of "dead" UPSs which you can pick up for very low prices or free which you can resell with new batteries. Supply the Serial and USB cables for monitoring.
Selling the batteries.
The second part of the business is you would have to identify and test battery suppliers from china and create a complete range of batteries of the same specs that the original manufacuter does. You would be able to far better rates than APC etc.
You could sell and deliver.
For those that are too scared you could provide the service of installing or collect the UPS fit the batteries and do the proper commissioning procedure.
Battery disposal & recycling.
Normally you have to pay for batteires to be recycled. It would be good provide a "GREEN" angle and solve this problem for customers.
It is quite niche but I think it is sustainable and something that you could build a reputation relatively quickly. Even geeks like me don't enjoy yanking batteries out of UPS and would rather pay for it to be done but not at the rates the original manufacturers charge.