Hi,
What everyone has said is correct...you can buy less than 150 if you buy resale. Disney will treat you the same as a "full" owner, but it will be tough for you to accumulate enough points to trade through Interval International, which only accepts full week exchanges. Other than that, there isn't a downside.
You really should be able to get into a small package, with closing costs included for under 10K, in my opinion. Contact your broker(s) and tell them your needs...they should advise you and call you with any packages that fit into your parameters.
Good luck!
Shontell