I'm giving a lot more credit to their last 5 years too than ancient stuff.

Other than that possibility, floating seems like the way to go.ALSO, in the house I'm rehabbing now, we pulled up the ancient carpet and found even older glue down tiles (possibly asbestos) in portions of the house. 

I don't know why I have to tell grown folks to occasionally wipe appliances down and keep them clean, but there ya go.The poor unit is only two years old but it's starting to look like the ancient thing I pulled out of there when I redid the kitchen.

I've heard of some just using a % of the deal value, but would be helpful to hear some actual methodology from some experienced folks out there.I'd appreciate any insight on this subject!

Even if plumbing is all new in the building if main is bad from the street to the building you can have water pressure, leaks in ground, and back up issues.That doesn't even get into knob and tube wiring, lead based paint, asbestos, old heating and cooling systems that are now outdated and must be replaced, ancient water heater systems, unpermitted or grandfathered additions over the years, etc.Ask the owner if they have a recent engineers inspection report of the property they can share with you.

My opinion... get your own real data and stay away from reports with faulty methodology.

@Nancy Bachety has a good methodology as well, but also make sure to check local regulations and laws. 

I've been investing in stocks, which has been okay, but it's increasingly risky as the market seems to be saturating on imagined returns.My goals are to be able to afford a much better home than the condo I currently own and to visit ancient spots in Europe to inspire an eventual writing career (or similar) once I have enough to not need a full time job.  

King Solomon, the wisest man of the ancient world said: “Divide your portion to seven, or even to eight, for you do not know what misfortune may occur on the earth.”Ecclesiastes 11:2Those words are just as accurate today as they were over the centuries.

@Ryan VanDuyneThere is no hard and fast methodology for assessing multifamily neighborhoods.Nonetheless, there are a few things to consider: Median household incomeMedian property valueGoogle street view and take a tour of the neighborhoodLocal amenitiesStrength and diversity of local economyCrimeAlso use the MLS and Realtor.com to get data on listed propertiesListing agent to get documentsSome good online resources I use: City-data (extensive database)Rentometer.comPadmapperZillow/Trulia/Redfin: good for SFRs + reports/tools.