I read about them on the web, but am very skeptical.

I finally have phase one of my web site complete and am putting the URL on some of my marketing.

I haven't looked, but I bet there is one available here on BP.Finally, the AIA (American Institute of Architects) publishes guides you can purchase that give you all kinds of figures for calculating costs.  

I bet I regularly work 80+ hours a week right now and love every minute of it.

In a web based society, what is the economic justification for the middleman when the seller can contact the buyer directly?

I would be happy to assist you and contact the buyers I am most familiar with to make the deal happen for you I also have a web site with a great deal of information for you as well.

If you're looking for theories of money management that could work that require more attention and judgment, that might work if you do something, my bet is that your interest only plan will fail in reality,.

Bet if you goggle "notes for sale" you'll find them

In my area I find a lot of 6-flats/6-plexes that do not have central air, despite the fact that it is a feature which is highly attractive for prospective tenants.When I try to search the web, including BP, it seems that almost no one talks about putting in the money and effort to install central air in these units.

While you might find a regional bank or credit union willing to sell you notes, I think your better bet is to work with someone who has a Dealflow of notes and can educate you on the ins and outs of the business.