How to turn Flippa sales into leads?

I've been selling on Flippa for a few months, and I've had some success. I'm mostly selling low priced starter sites, all PLR or Amazon affiliate sites. The prices are low, but I'm bringing in some money. About 2/3 of my sales are to IM noobs. I'm trying to think of a good way to get some extra cash out of my sales. So far, I've been pushing web hosting packages to those without it and I've made a few hundred $ this way, but I know that building a list is real way to make a continual profit. I'm just not sure what the best way of going about it is. I have two ideas.

One is start an aWebber or other mailing account and just invite people to join. The other is to make a membership site and fill it with PLR marketing articles and videos, and maybe some original stuff if it seems worth it. I've looked into it, but building a membership site seems like a lot of work and there's probably a lot of cost involved with plug ins and probably Amazon S3 for video hosting.

If I do the second, do I need to have mailing list also? Or should all promotions be done through the site?

Are there any other good way of making extra money I haven't thought of? I'm willing to invest some money into it, but free or cheap methods are appreciated. Most of the money I'm making I'm setting aside for my up comming wedding.

Any idea if any of this is against Flippa's policy? I don't want to get kicked off, I'm doing well so far and I'm already a super-seller.