But yes long term I am interested in buy and hold single and multifamily. 

We have sold (tax free), kept as long term and/or short term rentals as well.

Much better as a short term acquisition strategy for flips IMO but always a high-risk strategy that should not be practiced by anyone who doesn't have the liquid capital to pay off the loan if needed.

Once identified, we negotiated favorable terms by emphasizing a fast and hassle-free closing.

Reason being HML's are typically short term loans that are interest only.

Try not to get locked in too long 4. we're not necessarily looking to go "all out" in terms of theming, but if we did, what kind of revenue does that bring/ROI can you expect, and which Renos for theming are best to do from a cost-benefit analysis, and what do they typically cost?

The technical term is Sound Transmission Class. 

Does anyone have any advice on effectively setting up temporary battery-operated cameras on a long-term rental property to deter break-ins and squatters while rent-ready repairs are being made before a tenant moves in?

An easier route would be to convince him to go in on the short term rental together in a partnership. 

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