My question though is that if the most recent property tax is based on the previous sale price, if your purchase price increases dramatically then wouldn't you get a huge spike in taxes?

Perhaps try an Asset-based Lender, who may lend up to say 85% of THEIR appraisal, but, I don't know if they'll still lend that same number of dollars IF your purchase price is significantly lower? 

I'm a real estate investor based in the San Francisco Bay Area.

I had not had any problems with them before and I had qualified them based on the husbands income, so I did an addendum to remove a resident and had them both sign it.

Hello @Jeremy Geyer,Do you have rental properties near Jacksonville or the Little Rock Air Base?

I'm considering walking away from this deal but the property is about due for a price drop based on days on the market so I want to fully explore my options before we walk away from it.

I don't understand why you were told to prefer NC over SC just based on property taxes.  

I would have your agent pull comps of other similar properties and see what the market value of similar properties would be and base my offer from that.

Split the net profits on the venuture based on the amount they contribute.What are several other ways (methods/techiques) we can help or work with  potential investors?

You may get a line of credit based on your credit but this is no where near what you could get under a HELOC.