No its not common, however RE is all about math, if it makes sense to pay them then do so. 

Has anyone used a business line of credit to put money down on a hard money loan to buy a flip?

Since tenants pay for utilities, no sense in adding solar cost when you wont see a return.

Carrying min deductibles as an investor doesn’t make sense, so don’t pay the extra premium for it.

The competition for affordable cash-flowing investment homes is fierce, everyone wants the same thing and there just isn't enough of them that make sense.

many HML will call themselves private money lenders to give the illusion of cheaper rates and easier terms.Private money is just that individuals with funds to invest that are Private they dont hold themselves out as in the business of lending.normally this would be friends family or other high net individuals you may already know who want to do deals with you.

Brought up by a father who owned his own construction business my entire life, I know the trade well.

If the tenant makes sense, the rent is there, and it all works for the particular property, I'll go with S8.But I'm not the type to turn down a well qualified cash paying tenant simply because I only want S8.

Those hours went into learning the business.

That strategy actually does make sense to rent it out for at least a year and then sell it to recoup that fee of the GC.