If I were to buy a LI property and engage a PM who has experience with low income properties, do you think, I can mitigate some risk?

You have up to 60 days to move in, like @Chris Mason  said, but you have to live there for a full year after you move in.There are mitigating circumstances, such as a job transfer across the country.

An umbrella insurance policy may help mitigate risk but I'd talk to an attorney about my liability and then to a CPA about tax structure.

What would that rehab cost with mold mitigation, possible foundation issues and who knows what can pop up with plumbing and electrical when and if you open up a wall??  

I'm 29 and own a few rentals out of state, flip homes in SoCal, and am a partner in a loss mitigation / real estate company. 

I learned the hard way that a lot of this could have been mitigated by being better prepared and having the ability to set expectations clearly from the start. 

They don't care about the condition, just mitigating their losses.What you need to decide is if the price you offered still works for you and the work that needs to be done.

Many if not most of the homes in the area have radon/ vapor mitigation systems in the basement. 

Maybe you could mitigate them by diversifying a bit: maybe instead of the lower cost (40-55k) ones you said you're in maybe start to look either at a different 'class of properties' (which might require a different source of deals as well, like say probate/estate deals) and/or look at maybe investing in a place or a different way that would handle a downturn better like: (and these are just spitball ideas, not suggestions) but maybe like in a destination city, or in destination city with AirBnB-type rentals, or a military area, or a really popular/strong college town for investors which may not 'dip' as low in rental demand or something...just something to consider. 

you can get cash flow on the big island why not look there owing rental in Hawaii were you have no hvac to worry about mitigates a lot of issues.