I'm planning to purchase the SFR with a conventional mortgage, but my mortgage broker and underwriter are telling me this will create a lot of issues both legally and with the bank once I demolish the property and try to subdivide; since the mortgage is for the full property. 

Think about going to see there office most lenders do the appraisal and when its done they charge you .. they dont have you send the money up front.. but maybe some do.but worse case scenario if they don't fund your only out 950.00 but many do this and also have non refundable EM thinking the deal is going to close and they lose that as well. that's why reputable lenders are very important to keep you from losing 1 to 5k on a fake lender or more  and again I have no clue about this company.. just say in  how the fake lenders operate and what your risks are 

(Mortgage fraud…?)

Private money lender How did you add value to the deal?

I'm not only a lender, but we've been doing new construction in the Tampa Bay area for many years.

I have good personal credit (~730-740), average-high personal debt (mortgage, student loans, vehicles,) and I am employed making $90k/year.

Most lenders wont lend with out title insurance and time to underwrite, so wo t loan on auctions.This is the market I work in in  WA state, best of luck and don't go over your $ number! 

Our interest rate is 2.8% putting our mortgage at only $1,880. 

My mortgage is 200k.I want to buy a new property for sale that is commercial/resort zoned.

An investor should still research property taxes, insurance and figure out the projected mortgage payment - to calculate each property's projected ROI and CoC Return - before buying.