This has been so drawn out with waiting on Mother Nature, but I want to do this right.I had a gas leak at the line for my stove and at the pilot for my water heater. 

hard to do renovations without running water: wet saws, cement, grout, paint, dirty tools, subcontractors when nature calls, etc...

Challenges?

Always challenge the property taxes.Cash flow is not the only benefit.Tenant is paying your mortgage and paying down your principleTax write off on property taxes and mortgage interestSome appreciation in property value but I do not count on it, it’s a bonus when it happens.  

Has anyone successfully challenged an Appraisal and received a higher appraisal after pointing the right comps to be used?

I challenge common logic that stocks will always go up.

When you get into larger properties I have seen maybe 75 to 100 basis point spreads movement over the last 12 months.The article you posted is more general in nature.

My current tenants which were inherited when I bought the property are moving next month..So now the real challenge of being a first time landlord is approaching, and my biggest concerns with screening are:Evictions and Criminal Background - How do you check for this?

There's nothing wrong with taking on a modest fixer-upper in the beginning and taking on more challenging ones as you become more experienced. 

this is a challenging question because there are so many different variables. the important question is what is the investors goals?