The house will need new interior everything - plumbing, electrical, kitchen, bathroom, walls, etc. 

The electrical?

This is critical early on when you start investing.Better Property Management: Understanding the basics of plumbing, electrical work, and other home systems means you can quickly address minor issues before they become major (and expensive) problems.

Has the electrical, plumbing, or HVAC been disturbed in the work that's been done - or will you need to get into it to complete the work?

Value is being added by doing a full gut to the property, new mechanicals (plumbing, electric, and HCAV), as well as new cosmetics throughout.

They have been good as tenants, but I'm charging well below market with the agreement that the units are as-is and non-residential.The building is partially renovated, partially demo'd, has ancient plumbing and electrical.

However, some local jurisdictions may mandate it.Additionally, bedrooms must meet certain electrical outlet and lighting requirements, cannot have openings directly into a garage, and with some exceptions cannot contain gas appliances.

However, the legitimate issue was regarding Electric.

It is my understanding that you cannot use the ADU for short term rentals in Los Angeles.https://therealdeal.com/la/2019/10/29/while-you-were-sleeping-la-bans-granny-flats-as-airbnbs/If you make the ADU all electric (like I did on mine), then you don't need to worry about splitting the gas. 

I have about $300 on my credit cards (just finally paid them off for the most part, and have about $20,000 limit).My cash on hand is relatively light, but what my plan was was to find some single family homes in the north Detroit area (currently anywhere from $40-$60k and put about $15-20k tops into any repairs or fixes (not looking for total rehabs, mostly something I can do some small repairs here and there and paint, personally I am knowledgeable about renovating up until complex electric and plumbing).