Nearly all worked full time jobs that involved substantial time commitment while building their portfolio.

I highly doubt that will happen if they've been there for a substantial amount of time already; they're more likely to scoff and refuse to sign a lease.

DEFAULT: If buyer shall default on its obligations hereunder and suit is brought to either enfore or terminate this contract, the parties agree that buyer has made a substantial down payment requiring judicial foreclosure of this contract.Can someone dumb that line down for me?

Also in most cases owners are more than happy to sell for a substantial discount in lieu of prepping the asset for sale (cleaning the house or garage, listing it with an agent or generally talking about pricing or math).

Summerville's prices have increased substantially, so there aren't a ton of -100k properties in that area.

Banks typically require 20-25% down for investment properties and that can be a substantial amount of cash.

You may have enough to get beyond that gate and get people interested in taking your money for a substantial return.3.

If you are able to prove with substantiation that you spend 750+ hours actively managing your properties then you will qualify for active losses.

If your home has substantial appreciation, it makes a lot of sense to take all the gains free of tax. 

Qualified residence interest means interest paid during the taxable year on either acquisition indebtedness or home equity indebtedness incurred to acquire, construct, or substantially improve a "qualified residence of the taxpayer".