I tend to look on SFH if they cash flow $300 or better its a go regardless of predetermined ratio numbers.  

You mean an auto-withdrawal from their bank account on a predetermined date?

Is it something that is predetermined if so can it be negotiated beforehand?

@Matt HoneyfordHey Matt I am sort of in the same boat as you as far as my destiny is predetermined by someone else.

After consulting my CPA he advised we pay ourselves through "owner draws" We do this by simply writing a check to ourselves. for the agreed/predetermined amount each month. 

Hi Jason,My understanding of this situation is that the owner wants to sell you a stream of pre-determined payments.

You definitely will want to have your rental criteria predetermined and ask targeted questions to potential tenants before showing them your property.

I would offer them packages.  1) a predetermined (you pick) place to stay funded by you, plus a grocery store gift card to replace food and supplies needed for them to clean.  2) they can stay wherever and you will discount their rent based on a prorated rate and a grocery store gift card to replace food and supplies needed for them to clean. 

As a cashiers check needs to be a predetermined amount, how do you go about doing this if you don't know what the final purchase price will be?  

You would then separately enter into an option agreement which, in exchange for a consideration (option fee) provides them with the right, but not the obligation, to purchase the property at a predetermined price (strike price) at a set time (option/exercise date) in the future.You should keep these two agreements separate with no performance ties between them.