You could force the seller to bring it up to code before the sale is complete as one of the contingencies of buying it, let them deal with it.

If anything just buy motivating buyer lists or VA until you build your own buyers list.

If you're in Northern MN, there is a very good chance that the cost to build a new duplex exceeds the resale value, which would be an awful idea to build a new one. 

Investing is different from speculating, in that it’s data driven and therefor predictable and you have factors that play in that covers your downside and strengthen your chance of upside. 

There's a good chance the issue(s) you face has already been discussed and answered.Ask questions in the appropriate forum.

Based on all those factors, your best chance would be to partner with a more seasoned investor to get loans.

Sub2 is a risky strategy for a long term buy and hold as the longer the deal structure stays in place, the higher the chance that issues will arise (like issues with the loan servicer, insurance, seller filing for bankruptcy, seller dying, seller realizing their DTI ratio and ability to buy their next property is negatively effected and becoming upset about it like in your case, due on sale clause being called, etc.).

Investment Info:Single-family residence buy & hold investment.

What are the usual lending parameters for a person getting there first property with roughly a 700-730 Credit Score and trying to secure a home 200k or under?
 
Is there a way to have No money Down or Low money down? 

Chances are it will never get keypunched.