Also I have had the fortune of building rapport with many portfolio owners who allow me to help them liquidate.

Most people ignore this and gamble away.The pros are this is a time when money is liquid and values are high - better to get it now. 

Or if you think it's necessary, as some managers of large scale arrays lead us to believe (mostly to justify their position "managing" and array with no moving parts, or to appease investors who have little solar knowledge and just like to have something to point out and think it's important), then paying some guys to run around with spray bottles and squeegees for a few hours isn't going to be a deal breaker on a multimillion dollar system.

Benefits:• Money paid toward mortgage is as liquid as a checking account. • Lower risk and higher return (I think) than with aggressively paying down my home mortgage.• Lowers risk associated with a month or two without tenant payments.• Easy to leverage into buying another property next year.Costs:• High interest rate• Variable interest rate.

However, given that this building will be vacant at closing and I have the opportunity to sell all the old stuff within 1-2 days of closing, I wanted to get some advice on how fellow BPers were able to liquidate their assets' existing appliances/cabinets/vanities/etc. to help offest some construction costs. 

So, how can I not over leverage myself- yet get the rehab loan needed for the investment flip, and then get enough liquid for a downpayment on the next house. 

how much liquid cash do you have now?

There are times in the  market cycle it is well worth it to be liquid.

Just lower monthly payment allowing for more liquid cash to work with elsewhere?

You would also need to be concerned about liquidity.