Rentable Timeshare. You would be able to rent your vacation home when you're not using it, so it's only makes sense that you should be able to rent your timeshare.
Don't buy anything but a rentable timeshare. There's no reason you shouldn't be able to rent your time to others if you're not going to use it one year.
If the timeshare developer tells you it is not rentable, or has a bunch of rules that make it difficult to rent, walk away. It's your time, you own it -- so you should be able to rent it out.
Steer clear of timeshare developers who appear to be cashing in on unused timeshare by reserving the right to rent it out themselves. It's your time, you own it -- don't settle for less than rentable timeshare.
Of course, it makes sense to have reasonable rules to protect the property, just as you would if you were renting your vacation home. You are going to be responsible for any damage caused by renters. So rent your timeshare with care!
In addition to the normal rules regarding how many people can stay in your timeshare and the use of the grounds laid down by the resort, you should have a couple rules of your own and even require a damage deposit if you're renting to strangers. Be wise.
It would always be much more fun to use your timeshare yourself every year to enjoy a first class dirt cheap vacation, but sometimes things happen and you can't use it.
If you have rentable timeshare, you can at least get something out of the time. Obviously, it's part of the overall value.
I do hope you can always use your time instead, though! That's what it's all about!