Converting it might not be an issue but will sure be a process.If your property is marketed as a Duplex, make sure the seller provides an L&I cert showing the use of the property as a two unit property.

I'd highly recommend finding a real estate agent in your area that is investor-focused and they can help you run numbers on deals and provide some mentorship. 

The seller provides the house, they fix it up and when it gets sold, everybody gets the shares agreed to.I don't know what happens if the owner changes his mind and won't sell or what happens if they go over budget and lose money or what happens if the “investor” runs out of money before the job Is completed or if the rehab work is shoddy or if someone gets hurt on the project, among other concerns.

I would first try to increase your income/liquidity or bring on other investors who can provide the capital. 

@Margaret MirasolaWe created a "Deep Dive" series here on our BiggerPockets blog about Metro Detroit cities, City of Detroit Neighborhoods and comparing Metro Detroit to other hotspots investors usually consider: https://www.biggerpockets.com/member-blogs/3094/99854-deep-dive-into-metro-detroit-cities-ecorse We're not aware of any other property manager, agent, turnkey provider, flipper or wholesaler that's made the commitment to do this!

Are there any credit unions who provide HELOC on investment properties?

Maintaining detailed records of mileage, receipts, and other relevant documentation is crucial, and your CPA can provide specific guidance on this.

@Carrie Matuga I got a DSCR loan and went through Rent to Retirement who provides turn-key opportunities. 

Getting financing in your name and moving to LLC I have been advised does not provide true asset protection.

We can comfortably provide a down payment over $100k, have a few hundred thousand in assets (i.e. equities, no property), have good credit (both over 750), no credit card debt.