This is also something I read in the bigger pocket book that I invested in over four years ago lol, but thank you for the refresher.

but it's really, really tough right now as there is limited inventory, tremendous competition for deals, money is expensive, and good contractors are booked up.the equity in your home is an example of very expensive money. 

I have put better systems in place after reading  Brandon Turners book on managing rental property's, which has given me the confidence to dive into multifamily. 

Scott’s Book on estimating rehab costs.

Though, it's been a far better education than any book or course on real estate.  

Enforcing criminal laws on the books is what the gov is for.

For example, you can show the services you performed and the approximate number of hours spent by using an appointment book, calendar, or narrative summary.Doesn’t even need to be contemporaneous logs. 

Have you read the two best wholesaling books by Jamil Damji and Todd Fleming?

Pace Morby and others have groups/books/podcasts/etc on this topic. 

If you are doing this for accounting purposes, maybe look into some kind of software like Quick Books.