If so, do I use my personal bank account to apply for a loan or do I need to put money in the business bank account? 

If all in around $435k, wouldn't she need to leave money into this deal with a projected ARV at $500k?

Real estate investing is forgiving; the average person can still make money even with some big mistakes.

Some investors use conventional loans, while others use private lenders, hard money loans, or partnerships.

They'll want all the money spent on the main house, lenders kind of ignore ADUs it's weird. 

I'd rather have a property remain vacant to I can spend time cleaning up and getting it ready and back-online so it could be available for someone else to rent.

If you decide to revisit STRs, you might want to explore properties where you can project expenses independently, such as using local STR forums or online tools to estimate maintenance, management, and occupancy costs.For networking and strategy-building, you might find local meetups or groups beneficial.

Just try to sell it to someone else for anything so you don't lose all of your money.

Now we are mostly scaling our business with larger communities but I've used many different creative finance strategies including seller finance, private lending, hard-money, collateral from other properties, and lease-options. 

I will not have a full time job until this comes, so I wont be able to show much income other than part time money flowing in, until I start this position.