This county is stating that the starting auction amount can only include the principal amount of the certificates which we have paid over the last 4 years, but cannot include the accrued interest or the auction fee the County charges investors to start the process (which total ~$4,000 in this case). 

Did they post a security deposit with the current owner? 

She already put down a $4k deposit.

Using some sort of a sinking fund factor can help estimate the amount of reserves needed for upcoming capital improvements, which factors in anticipated growth attributed both to principal deposited and interest earned.

I often tell folks mgmt is like an insurance policy, sometimes you get lucky and we do a ton of work for the small amount you pay us and you get all the benefit, sometimes you don't need alot but we are there ready to help when needed. 

I figure I'll have everyone pay a deposit and sign a lease to book it and hold a spot on the calendar.

No amount of clever advertising or photoshopping pictures will get you over that. 

If you do offer the first month's rent 'free', I'd take an additional month's rent as security deposit. 

@Harsh Patel for your learning journey: I would consider a person with 1 eviction IF: They explain why the eviction happened, I saw a financial hardship event of causation, something has changed in their financial capacity since then, they pass all other criteria, they post minimum double security deposit and pre-pay 1 full months rent and retain a pre-pay of 1 full month rent paid for 1st year tenancy. 

Mistakes are inevitable in real estate, whether it’s a missed repair in underwriting, a contractor who walks off with a deposit, or poorly executed work.