When do you stop renting and buy?

EBay started its Partner Network today. This is its affiliate program. EBay had been running its affiliate program through Commission Junction, but is terminating this relationship within a month or so. It's easy to understand why: eBay now owns its affiliate program rather than having to rent the service from Commission Junction. I don't know the specifics of the deal between eBay and Commission Junction, but certainly Commission Junction wasn't doing it for free.

I recently purchased a serial autoresponder script. This is a script that lets me automatically send out a series of e-mails to people who request it, totally hands-off. It cost me close to $200, but I own the rights to install it on up to ten URLs.

It seemed like a good purchase at the time, but now I'm not so sure. It's not a bad script by any means — it's one of the best available, actually. But there are services that would let me do much the same thing for only a small premium per month over what I'm needing to pay for hosting this script. As I get more subscribers, the cost goes up for the service, of course; instead, I own the script. But I'm also out almost $200 right off the bat. It probably would have made more sense to rent the autoresponder service first, then buy the script when the cost/benefit made sense.

Entire businesses can be built using rented equipment. I heard recently of a couple of guys that do lawn aeration using a rented aerator. They sign up enough customers to fill up a day's work, plan out their route, rent the equipment (even the trailer!), knock out the jobs, and return the equipment. They don't maintain the equipment, and as long as they don't break it, it doesn't cost any more than the day's rental. Pretty slick.

Buying equipment or owning something usually makes sense at some point over renting that equipment. But not all the time, and probably not right at the start.