What is the structure set up?

You will not get them to show up to complete the work, you will not recover your funds and you will have to move heaven and earth to make this "right" 1-See if you can settle with the contractor2-File complaints with the BBB (assuming they are registered), file a complaint with the state attorney general3-SueI used to believe there was some sort of over arching justice in the world, but then I got into real estate and became friends with RE attorneys.

The timeline depends on the product you use to do your refinance back out (after buying all cash with no liens).

Involve the agent you choose to list the property.7) Get the work done.

(probably the biggest key).

@Jacque Mihovk what can you buy with the funds available, assuming 20-25% down payment and financing the rest?

Especially if you get a long term resident in the ADU and then you might can utilize them to help on your turns of the MTR. 

I question how much value above costs can be achieved.An ideal BRRRR has zero costs and has positive cash flow after the refi to extract the value add.  

Lend $100k on a deal for typical terms, but with the option to convert your loan into an equity stake in the future?

If they wanted to send a hard money pre-approval for half of the purchase, then either A) the lender needs to confirm that they verified the borrower possesses the remaining cash to close, or B) the borrower needs to show proof of funds for the remainder.