People simply won't easily buy a house with previous hystory of crumbling foundation even if it is fixed... or "claimed" to be fixed.The 70% rule also doesn't account for the projected time it takes to flip a house.And no... your predetermined "holding cost" incorporated in your 70% rule is not it.The 70% rule is a death trap and is a sure way to derail your business.Also, if we are both interested in the same property, and you give a 70% offer, you will ALWAYS be beat by me that will ACTUALLY give the highest possible offer I can make. 70% rule focuses on being "safe" and will have the effect of not getting many deals.The right method focuses on property determined risk analysis to leverage "being safe" with the amount of allowable profit (for that safety margin). 

Then we could split the money at a predetermined percentage when we sell.

According to the complaint, some financial services companies "lease" funds to customers by opening bank accounts in the customers' names and depositing funds into the accounts ("leased-funds accounts") for a predetermined period of time.

HI Jon,It looks like 75% cash out on the rental would be around 4.250% on a rental property condo and cash out  so that means you'd be able to access about 145k in capital (prior to closing costs).A conservative route may be to take the lower 4%'s 30 year cash out since the payment is a predetermined amount per month that won't fluctuate.As long as your new investment you make is earning a return that is higher than your increased payment on your rental property and earning enough of a return on what you're looking to buy you should be ok.Some say you should obtain a rate higher than the one you're borrowing at but the truth is the rate isn't all of the payment and in financial theory that sounds great but you in reality you'll want income that is in excess of the entire mortgage payment which consists of the interest cost and the principal portion too since this is what has to leave your pocket each month.

If they do not respond to your pay or quit in the predetermined timeline, I'd continue, as it's likely this will become a pattern, but you need to talk to a lawyer.

No need to get a lawyer but having a predetermined rate established with a lawyer who specializes in property law could be lifesaving in the future.

Tenants either pay when they get the court notice and realize I'm serious or tell me there is no way they can pay and give me the keys within a short predetermined period. 

I've heard of thermostats that you can restrict to a predetermined range.

While there is some truth to what's being said regarding homes being torn down at what appears to be a rather pre-mature time, especially in comparison to North American homes which may be in use well over 100 years, a lot of the information contained is reflective of theory - derived from a predetermined "depreciation" formula established by the government, in essence, to keep the economy humming.The basic formula was determined by taking the age of all the homes that had been razed, and averaging out their age.

Once I hit a predetermined amount of reserves as others have suggested above, then the excess money goes to other things.