The pay at it was so low it wasn’t helping provide down payment money but it did cover my cost of living.

This could be useful information if you need to push back on this and you might want to consider floating some questions back to the landlord about the depreciated worth of the door and hint that you are not expecting to pay for a whole new door.  

If it needs to stay in the original account, can I use it to pay for other expenses?

This law applies regardless of whether the tenant volunteers to pay a higher deposit due to credit issues or any other reason.

Third, I'd like to know what data I need to collect in order to write this off on taxes.

An agent brought a property that would pay for itself and had the potential to increase rents and make non major improvements to increase rents.

Pay off the 700k bridge loan and you collect 125k of your 150k back so you'd leave 25k in.

Waiting a year might not be a bad idea versus pulling the trigger sooner and having to pay to refinance later.Also realize it may be tough starting off as a 17 year old.  

These are popular programs among investors because they do not report to credit agencies, use DTI to qualify, and do not require tax returns or income verification.You can use a DSCR loan to purchase or cash-out refinance, a strategy commonly referred to as BRRRR (Buy, Rehab, Rent, Refinance, Repeat).

Ask the questions...Maybe they want to avoid cap gains taxes so a small down would work.