do not use a line of credit for a down payment. 

With the exception of building a trailer on the property (these are hard to finance), this sounds like a good plan AND if you are using it for your business AND your business pays more than 50% of the rent (if you have more than 1 tenant), then this is a more financeable property in the eyes of banks and credit unions as it would be consider a commercial "owner-occupied" property. 

I have two banks that have done so as well as a credit card, and know of a couple of organizations that have as well.

If it is a credit/equity line, you could provide a lender letter that the funds are available immediately for funding - and cured any recission period. 

If you have nothing, and make nothing, you declare bankruptcy, wreck your credit and try to go back to renting.

At this point, I would recommend having a line of credit to cover these things so you don't have money sitting in the bank doing nothing when it could be put to work.I have 33 units, no debt except for mortgages, and excellent income.

Plus, if you aren't able to get approved with what you've got now in terms of savings, credit, etc. you can learn on what you need to qualify so you know what to be working towards. 

Usually the numbers don't work to build in these neighborhoods, unless government tax credits, etc.Do you see the problem with your two statements:"The turnover costs could/will be high"and"How much more damage could they do?"

You need to build your credit.

Once I sell that I’m gonna convert to a fourplex and do the ADU.going through cash quickly and also using credit cards when possible like to purchase materials.