Talk to your agent and don't try to hide material facts about what you're planning to do. 

@Kyle MasonTo increase your loan amount, consider strategies like increasing rental income, co-signing with a co-signer, using portfolio loans, negotiating seller financing, down payment assistance programs, paying down debt, and considering alternative loan products like DSCR loans, non-QM loans, and bridge loans.

The costs of land  , engineering , site work , permits , labor , and building materials make this virtually impossible . then there are zoning issues and the rest of the politics that go along with this . 

Examples would be incorrect square footage, incorrect year built, incorrect style of home or materials.  

I am building a vertical addition above the existing main level which would have vaulted ceilings OR alternatively the front half would be vaulted and rear where the bath/closet is situated would have flat ceilings with rooftop deck above.    

Alternatively, if there is no equity in the property do a friendly foreclosure between the LLC and you mortgage holder. 

I'd need to go to about 250K with 10/15K in materials to get around 320K and that's pushing it.

[Redfin]TP: This is really just an attention-grabbing alternative to saying that prices have risen a lot.

Also, an alternative would be to put the money into an escrow account then once you have documents, verify legitimacy.

As a seller, you HAVE TO and should declare anything that would materially affect the value of a property aka a fire.