I see why many of us on BP want to keep admin work to a minimum and reduce the necessity of extra entities and extra bank accounts, but these are things that the big players do. 

Similar for a shower with a proprietary enclosure and a Schluter system and fixtures which bear an enormous discount to plumbers and installers.Paying the GC on day one for these things does not reduce the risk to the GC unless it is established in the contract that materials are paid upon delivery to the site.

For those with higher capital reserves and down payment percentage, assuming a pandemic era mortgage (typically from 2-3-4% can dramatically reduce carrying or mortgage costs.

While paper equities had a great run in '23, I find the indexes very frothy and reduced out of those as well in my retirement accounts over the last couple weeks. 4 SS facilities sounds like a lot to sell. 

This may reduce rental prices further but it is hard to say by how much.

The reason I would wait until the non renewal is to reduce friction.

In addition to the high cost of building, the low appraisal reflects there are many more owner occupied purchasers than investor purchasers so adding the ADU likely reduces the buyer pool. 

But considering the way he does it sounds like a great way to reduce risk.

However, by doing so, I'll be paying $1000 extra each year towards my mortgage, reducing my cashflow to $4000/year.

When you do a cash out refinance its cash in hand (liquid reserve) so it can be used as an asset or for PITI reserves on the next purchase.The other downfall is if your credit score should drop for any reason which can happen even my accident or mistake the lender will close or reduce the Heloc credit limit.