One thing to note: I had this same Sealey tool and used it for a few years in the shop on a variety of upper ball joint EV jobs. I'm very careful with my tools and treat them as any professional would but the intense pressure at play during the use of this tool led to wear on the U shaped inserts that made its usefulness wane over time. I would estimate that it is good for about 5-10 vans (so 10-20 ball joints).
Just a point of reference for you Rob so you can better amortize the tool in a rental program. And keep in mind renting it out to the public also means it won't be in the hands of professional mechanics who do this stuff everyday, so figure in some accelerated wear/breakage.
To wit, there is a sign at our local machine shop that says: "Don't bother asking, we don't loan out our tools."
Justin
2000 EVW 5-spd TDI