Hi Bryan
Buying leads is a great way to build a list.
But the problem is they have to be treated different from you normal leads. coregs leads don't have the relationship starting off so they need to be soft sold until they really get to know you.
Just watch out as coreg is dirty business for the most part and you need to make sure you are doing opt-in and not opt-out sign ups.
Plus you will need a real time follow up system in place. With GR you are fine but they are slow in there lead gen.
Also make the target ad as specific as you can. Since you are paying for every lead make sure they are going to be the right fit for you.
Also look at PPC. This is were I get my best sign ups from. My Avg Cost per conversion is .32
Check out this image.
I'm getting sign ups all day for .32 of this campaign with adwords. It took a lot of testing and tweaking to get them down to this number.
This is going after some very wide terms of the CTR is low, but this type of setup works best.
Thanks
Charles