Plumbing, mechanical, etc. the works.  

I'll second the issue of a mechanic's lien.

Building a business based on that number will result in failure when the cows really come home and those big capital items start hitting. 

Yellow letters Walmart sells like a 3 pack and white envelops at the 99 cent store...walmart also has 40 envelopes for like 88c.AS FAR as learning how to wholesale...read a bit on bigger pockets to get the general idea and mechanics.

House when completed with have all new mechanicals, updated wiring, updated plumbing, new windows, new floor coverings, and new coat of paint.One issue (if anyone has any ideas I open for the ideas): In the basement we are scheduled to do interior basement waterproofing including new sump drain. 

Also if you are going to invest out of your area, make sure you have a GREAT team in place, this can make the difference of your success or failure very quickly.

Further reading but pay attention to dates of the writings since NEC has changed several times over the years:http://www.nachi.org/forum/f19/gfci-and-refrigerat...http://www.dslreports.com/forum/r27506429-GFI-outl...https://www.ridgidforum.com/forum/mechanical-trade...I'm sure if you search google you can find lots more discussion like this. 

I learned a lot through that failure/education experience that I do not plan to repeat this round with starting/growing a business. 

Think of it this way- I can show you how to fix your car, I can give you the manuals and even a shop to put the car in, but having tools and a manual does not make you a skilled mechanic.

In fact, this little realization transported me back through all the 9 years of trials and failures.