Working with an investor in Maryland who has multiple units for sale, could do seller financing on just one or bring in another person outside my LLC to try to buy everything to get the best discount possible.

You'll need to either call to small banks for this type of a loan or work with a mortgage broker - specifically, a loan officer that works with multiple banks. 

Nope.Also be very sure you want to involve yourself in events before you take a booking for something like a "small" wedding or "cozy" party. 

I personally have multiple plans-401k, multiple Roth and traditional IRAs, HSA, and several CESAs.

This may be something to consider as a multiple property owner.

You could sell one house and buy multiple homes if you want. 

Ours involve creation of notes, and then forgiving them over several years, to take advantage of the annual limits on gifting.As to the mortgage, you cannot just take his name off the mortgage.

Simple loans are good for someone early in their career but if you own multiple properties or something like that your loan might cause him some trouble. 

I don't want the offer to be contingent on the closing of my other place as I think that this property will have multiple offers and I don't want mine to look weak. 

I would NOT have settled for that ultimatum, my attorney would have been involved real quick!