You want an agent who will read the HOA budgets and meeting minutes and who feels comfortable making calls to the management company and HOA board members to get the lay of the land.

Double that contingency budget!

Make sure you run your numbers both ways.Include a budget for initial repairs.

criteria/budget/return expected/hold time, etc

The rehab budget got blown completely out of the water by "surprises" but that's half of the fun of any good learning experience, isn't it?

Does your pro-forma include a development budget with all soft and hard costs included as well as an operating budget, equity cash-flows, sources and uses of funds, lease-up time table, sales proceeds analysis, etc.? 

If you don't own the 20 units yet you can either budget for the CAPEX or you can speak with your lender about doing a LTC where your rehab money with be incorporated into the loan.

I am planning to buy a fourplex property as investmestment property, my budget is 200k downpayment.Any recommendation as to where i should buy the rental property?

A capex budget needs to include but not limited to: roof 25 year life span, floors 10 year life span, appliances and hot water heater 12 year life span, hvac 20 year life span, bath and kitchen remodel 20 year life span.

Please keep in mind that nothing is every really turn-key though and you should maintain a repair budget just in case.For question #3, just being on BP and learning from other savvy investors is a start.