Happy to share what I use for estimating rehab costs - there isn't a fool proof way to do it but it comes pretty close considering you'll want updated pricing for line-items regularly verse having to do a bunch a work to research recent prices every single time for every single property.Always your best bet is to create a scope of work - as mentioned above, a list of all the obvious items that need attention that you can visually see or know from an inspection report.

Definitely what I would call a base hit for my first deal; a home run would be great, but I didn't let perfect get in the way of good - remember the first one is hardest one to get.Now that being said, some people may argue that my maintenance, vacancy, and capex budgets are low - and they may be for some areas - BUT I'm fixing everything found in the inspection report and installing a ton of new stuff with an emphasis on reliability... not fool proof but I think it increases my odds. 

The middle: The foolproof approach and the most expensive.

The way I've done it is have my realtor ask the listing agent if they are allowed (again, not fool proof, but a way to get an indicator). 

Nothing is foolproof but you have more protection through an LLC and you have even more protection through a trust.

If you're going to go the partner route, be sure to keep a controlling interest - either 50.1% or have some foolproof partners (i.e. your mother, for example) to give you enough control over disposition of the asset. 

And while nothing is fool proof, that should help limit your risk here.  

It is essential that you get an absolutely foolproof rental agreement.

It is my belief that no strategy is foolproof and some can be counter productive.  

I worry about the liability, but I don't feel that hiring out the snow removal makes things foolproof enough.