For example, look for homes that have tarps on the roof, bad paint, lawns that haven't been mowed, trash in the yard etc. 

Unfortunately, unless people start questioning these type of discrepancies in "expert opinions", some people in this country will continue to suffer from this type of artificial devaluation of their properties.

The only problem I ever had was lawn maintenance. 

The front landscaping is done but the backyard needs sod laid and mulch, I already have my weekly lawn guy and his crew on standby for that.

I hope someone can help with what kind of big expenses  are in the multi family properties i need to know when looking for properties(can only think of roof, deck, insulation , heating system )Also, Not sure if I jump ahead but I am trying to sort out all the related expense for rental property below with my conservative estimate per yearProperty management fee (10%)insurance :2500property taxes: 2000 -3500Owner paid utilities : 2500( in case of paying oil burning heating system , if tenant pay their own electric heat so i guess i can eliminate this expense)snow/lawn: 1200Accounting cost: 100Vacancy reserve (5%)Maintenance reserve (10%)Can anyone give the idea if i include these expenses correctly ?

Yes, I am ready for them and believe you are right))) HOAs suck, but owning a Multi Unit for past 8 years, there are cons to those as well, like major  Roof Repairs, basements leaking, building plumbing issues etc , lawn mowing and snow removal costs and higher taxes,  those are to consider as well.

Example: you hire someone to mow your lawn.

If you’re with a partner who is creating artificial barriers to sound investment decisions, then it will be on you to work on your partners frame of mind, or, to reconsider what partnership means to you and what kind of sacrifices it ought to come with.

You may have your own sewage treatment plant .you will need to buy a large tractor with loader, a small dump truck , lawn equipment , golf carts for employees to get around .Build a house or 2 for management to live in . 

A condo may seem like an easy win: no lawn, no exterior maintenance, outside is always kept up, they have rules to keep tenants in line, etc.In reality, an HOA is only as good as the people running it.