I am looking for best practices both from a legal protection standpoint and from a tax advantage standpoint.

Verify if there are any outstanding violations or issues that need to be addressed.Financial Analysis: Review the property's financial records, including income statements, expense reports, tax assessments, and utility bills.

I have investments in Loudoun and one in Clarke County doing extremely well but bought everything in 2008-2013 and have been hibernating since..looking further out in Charles Town WV specifically because of location closer to Northern VA also the taxes are cheaper.  

I think some markets, mainly the STR runners, have another 10-15% to go then the markets hit by HOA/HOI/Taxes still have a bit more correction to go for. 

I'm not ruling out Florida, but it isn't my focus because of taxes and insurance costs.

What do you use for bookkeeping, accounting and filing taxes, as you start up?

The owner typically pays this as part of ownership, just like taxes and insurance.

If you're in So Cal, the closest neighboring city with better property taxes (they don't reassess on the sale), landlord laws, prices, etc. is Nevada (particularly Vegas). 

You need first to verify they are okay with this.You must be very careful since if any investors are "passive," it becomes a syndication, and then you must consult an SEC attorney.It sounds like your investors will pool their funds together (they probably will create one LLC) and become a 2nd position lender.

Is there a tax strategy for using capital gains off the sale of a home to pay off other homes in your portfolio to improve cashflow?