Kelvin
Check out www.vacationclub.com. It's the Marriott timeshare site. The Marriott time shares are floating weeks so you're not locked into a week but a season. You can put your unit/week back into Marriott inventory every other year and receive points (about 110,000/2 br unit, I think). If you buy from Marriott you will get extra points and probably free Interval International membership for a year or two. I've heard of other owners receiving free weeks at Interval properties.
If you decide not to purchase a timeshare and go the hotel route, you can rack up Marriott points in other ways. Get the Marriott reward charge card as previously mentioned. Also when in residence at Marriott's, spend money at their restaurants, charge to your room and receive points that way. You can do this as a timeshare owner too.