An infinite return for the rehabber because they did not put any of their own money in the deal.

You are missing a shelf in the cabinet as well. 

Is it common for individuals to buy a shelf company or an established company?

It is a hollow door and if I could buy it off the shelf and install myself, it would cost just $46.

If you want to scale borrow; if you have money on the shelf and can easily get more then there is no harm in using cash; just never run out!

A fully operational hand off short term rental with positive cash-flow and after the cash-out refinance at 65% LTV, yielded an infinite return.

This refinance, if it is a cash out might increase your cash on cash returns because if you get some or all of your original contributions out you may have up to an infinite return.Why would you put 0% down when making your assumption or what are you trying to get at when doing that?

Guess you could put a small shelf under it for now to make use of the space.I don't see the problem with it, but the person who is moving into the home (a friend of mine) is freaking out over the panel box being relocated to the outside.

In my market this employee will have infinitely more knowledge of this business than you do.

We stained and sealed them for about 50% of the cost of the off the shelf prefinished cabinets.