Most lenders are going to be limited to using the lower of appraiser's opinion of market rent or the actual in place lease (or in some cases 110% of market if lease is greater) so it sounds like you just need to roll the dice on a new appraisal but I'd recommend having some rent comps on hand for the appraiser up front just to avoid the same issue.  75% cash out pending positive DSCR is widely available at most DSCR lenders. 

You essentially have essentially cast a super wide net and are going to get a ton of sales responses, but what I gather from your post that what you really need is a mentor/like minded investor to help hone in on recognizing good deals, narrowing your focus and absolutely protecting your capital.   

It's a big decision, and it's smart to consider all angles before diving in.You're right to weigh the current market conditions and potential future trends.

Typical bridge loans offer anywhere from zero to two 12-month extension options, but this can vary widely depending on the specific lender and deal characteristics.

That all being said, I really don’t think open concepts or great rooms where the kitchen, living, and dining areas are either wide open or visually connected is going away at all. 

Marketing Strategies: What’s the best way to market this property, especially with the creative financing angle?

In addition there are a wide range of grants HUD supports in most cities to improve a property to rent to low income people.Perhaps the best decission in looking at section 8 and low income rentales are the larger assets of using the contract incentives and special financing programs that only exist to those who provide services and employ your tenant that you could benefit from.

Now one angle (and I'm not an attorney) would be if the Seller knew the electrical work was illegal and didn't disclose. 

I'm interested in talking to someone about getting our nonconforming basement up to code to either duplex down or make it a legal unit if ADU ordinance passes city-wide.

Wall st vs main street is wide, and it's going to get wider before it tightens.