Choose an area and become an expert in this area - drive it all times of the day, look for homes that have characteristics of neglect - poor roof, un-kept yard, signs/notices on the window/doors etc.  

It needs a new roof.

I plan to bring a contractor to the showing to check out major things like roof, foundation, etc., but should I be wary of anything else?

Investment properties aren't cheap in SG relative to MY or IDMy two cents on Singapore's property market from an expat former banker perspective:-cap rates (income-expenses before financing relative to property market price) went through the roof since people see limited land--peaked in 2015ish, but still outrageously low-interest rates dropped low enough to sustain borrowing on these low returns-building has continued without parallel demand growth (supply>demand)-Singapore employment regulations are being more and more protectionist (and an ageing population) so you won't see foreign labour growing significantly in the next 5-10 years IMOPersonally, I would be more interested in Indonesian office/industrial/MF just from macroeconomic factors, but there's opportunities in every market if you find the right niche.

You should have your own criteria, run background checks (always, but especially when putting two strangers under the same roof.  

You water damage could be from a roof.

Imagine a 15 year old roof. 

New roof newer furnaces and electrical.Purchase price 107000Estimated rents total 1425 Taxes: 2800Insurance: 80 per monthWater/sewage estimate: 200 per monthGarbage estimate: 20 per monthPmi:73Gas/electric paid by tenants.Vacancy 5 percent:71.25Maintenance 5 percent:71.25Cap ex 8 percent:114Cash flow:$84 The rents are estimated because it was used as an in-law suite.

Ideally, I would like for my "team" to have all of these positions, firing on all cylinders, under one roof.

I was told a new roof was put on in the last 5 years and all utilities are separate.