I'm pretty risk averse so I like to have room for the unexpected.

My first question was do you have all your components in place; i.e. your contractor, your ARV, Rehab budget, materials?

Had I used your Rule of 5, I would have bought both of them and had multiple tens of thousands in unexpected expenses. 

What having cash allows is for three things:1)  The ability to pay for unexpected expenses.2)  The ability to quickly act to take advantage of good investment opportunities.3)  The peace of mind knowing that you can do #1 & #2 because of your cash position.

Unfortunately, the expenses are still variable and are always unexpected is such properties - the price of a roof, hot water heater, or air-conditioning compressor replacement will be about the same, regardless of market size.   

I have seen this fubar people when they spend 95% of their IRA funds on a rental then have unexpected expenses and do not have the reserves and have already contributed to it for the year.what do they do in that circumstance Dmitriy is there a hard ship they can use .. or what ?

And I actually estimate 10% for vacancies and 10% for repairs to allow for unexpected contingencies...you'd rather be generous on your expenses to ensure you are still cash flow positive than to underestimate them and be cash strapped.

This includes understanding how to factor in any costs related to the components of the plumbing system which are not easily visable during a walk through, including, but not limited to, underground and outside components of the plumbing system.

Things will happen and unexpecteds come up.

This total is about 25%, so your 10% security margin seems low.At 5% down you would want a fairly healthy reserve fund for unexpected high cost maintenance or vacancies as you have very little equity available.As it is, you're catching a falling knife in Grand Prairie and it is certainly conceivable that property prices and rents could fall a further 5%+ over the next 12 months, putting you in negative equity and cash flow territory.