Lead purchasing questions...

So I'm new, and feeling the right amount of beginner's luck and hard-work starting to payoff...

I'm wondering though where I'll continue to pull leads from 2-3 months down the road, as my friends and family can only buy so many houses. I'm asking for referrals, but I'm afraid to slow down and lose momentum. I feel that a deal or two additional a month would drastically change my business, and get my moving forward with even greater momentum.

Does anyone in the community have any feedback on experiences with buying leads? Please comment with where you get them from, how much the cost, the quality of leads, and your success rate (if known).