The trick is dealing with an honest realtor who is looking for your best interest in the long run. 

Any tips, tricks, or suggestions?

If I bought it the "normal" way I'd need 20% of 5.9m (almost 1.2m)So this trick saves me $400k needed to close and means I'm really closing with closer to ~12% of our agreed price down

It seems the trick is to get in good with the developers and get them to have the exclusive right to sell the units. 

Likely, no, at least not in the way you've spelled out.It goes against the grain to say, but the best way IMO to make passive money in REI is in market appreciation ... the trick there is in how to get into such investments in such a way as to still make money, or at the very least not lose money, in case you don't get the market appreciation, but those methods tend to NOT be passive, at least not in the short run.

Trick is you have to mail them time and time again. 3-4 weeks apart it will produce just keep mailing.

But the real trick there is that some of these people use the bankruptcy to lengthen the eviction and then get the eviction dropped and only show the bankruptcy.Still, if they haven't had a negative outside of the bankruptcy for 9 years, they'd probably be fine.

It's not impossible if you put in the time and effort to learn the tricks of the trade but it is the toughest in my opinion. 

Fortune Builders likely provides a good service, with valuable tips, tricks and training, but is it worth $20-$50k?

Make sure they know that you will do most of the work.If someone has been thinking about selling, but are overwhelmed at the prospect of fixing the house to put it on the market, your letter could just do the trick if you let them know what you will do for them.