@Gregg HuttonSounds like your patience and REI success has been very effective in getting your wife to take interest.

What's the most cost-effective way to find this information?

Have a home, so need mortgage interest off, 1099 real estate brokerage job too.Generally who is good with he NJ/NYC commute situation's tax effects and real estate tax savvy. 

In other words, the rent roll would effectively pay for the loan and be paid in full in 10 years.  

What's the most cost-effective way to find this information remotely?

I've heard people say to expect a call-back % of anywhere from 2-8%, and that seems reasonable as I'm already analyzing more houses than that monthly.Also, I've found a lot of good info on the site surrounding what to write on the letters and how to be cost effective when sending them, but I'm still unsure of how the negotiation process is going to go once a motivated seller calls me.

Again, this may not be effective when you start to get into higher ranges - see @Russell Brazil's point on $400k homes - but I have found this to be a good, quick, dirty test at anything sub $200k.

So the effects of supply and demand come in.

I want to find effective strategies to to get a deal in a hot market.

And if they are on assistance you may have to provide written notice also to that provider of any rent increase.the leases the tenants had prior to you buying the building are still in effect.