The problems could be re-piping zones and DHW pipes. 

They can be relied on to be stupid and to drop the ball, over and over and over again.

Rather than explain them here, for brevity's sake, you can search both terms on BP...Brandon Turner has video descriptions of them somewhere on the site.Anyway, both are are quick methods to get an initial estimate of purchase value if you know the total rental income for a property (for the 50% rule, I guess you really need to know expected/prevailing cap rates too to get purchase price), but neither should be relied upon for anything more than a starting point.   

@Eric Hyde what's up another Southern California member! I

Oh, and if you are interested in becoming a Pro member, I HIGHLY recommend you do so before next week. 

You may not feel this expense right away, this calculates vacancy, management, and long term capexAlso, you spent 450K on a non-investment house (EXPENSE), this obviously hinders your progressIf you're going to be relying on your own funds to buy these units, then yeah it's going to go slow.

The term of a tenants lease has very little bering on when a tenant will move.

Plus you won't have to worry if your neighbor will call to complain--and you will be re-doing the work to code in the end. 

But he will deny it since 12 years have gone by.Roofing rafters need to be  re leveled,  It is not that big of a fix and most framers will do it for about the cost of your deductable!

The tax write off the IRS gives you for pretending the value of your investment property goes down every year must be re-paid if you sell and the house has actually appreciated or not really depreciated.