I get kind of weirded out when I see folks leave their left over grounds. 

. - provided you can resist the urge to spend it instead of using it as intended.Yes, you can add to the principal payment amount every month if your budget supports that.Here's the piece that folks tend to gloss over: This method of debt acceleration only works if you have money left over at the end of the month after all your debts and expenses are covered. 

Vinyl siding also can warp,get cracked. get ripped off in high wind,sun will fade it and then leftover pieces will not match when you replace years later.  

My goal would be to get two of these with 25% down on both and still have some leftover to update my current primary residence to build forced equity. 

Quote from @Carlos Lopes: Gross income doesn't matter.This is the number most people post, and it's 92.7% useless.What you need is NET income, meaning the money left over after all expenses, and that should include a dollar amount for your personal time spent operating the business. 

The 150k is what's leftover after 30k/30k put aside for our personal and property emergency accounts.

I am also reading the section 1231 regarding net operating loss (NOL) and wonder if the leftover could be carried back on the last 2 years of tax return?

This renovation took 2.5 weeks for two guysScope of WorkDemo and gut entire kitchen, gut one bedroom, and partial gut of bathroomBuild new closet and frame out a wall to create a bedroomInstall new laminate flooring in two bedroomsInstall new subpanel and new electrical for entire apartmentNew (and some reused) cabinetsNew quartz countertopNew (but bought used) 24" rangeNew microwave and fridge (new fridge not shown in photos)New toilet, medicine cabinet and vanity light in bathroom New built-in kitchen table and chairsCost of Work (approximately)Labor $6,500Cabinets $2,000 - I bought some nice, used Ikea cabinets from Craigslist for a previous job and I had some left over.

I have a property that burned down and may consider doing an exchange (if needed) with cash leftover from paying off mortgage.Can someone send contact info?

By Fundamentals I mean, as an example, how much revenue does a business earn, what are its expenses, what sort of profit does it have left over to pay dividends or reinvest in the business.