But they'd better have some reserves available after acquisition costs because you can get bitten by the unforeseen. 

You need Capital for down payments, and occasionally you will need to inject cash into a home when something unforeseen happens.RE investing is a fantastic way to build wealth..

One issue I see is folks buying rentals with their IRA and tapping it out.. so when this stuff comes up they do not  have enough in the IRA to take care of unforeseen events.. so its doubly important if your buying rentals in the IRA to have a very nice amount of money left in the IRA in liquid investments. 

And finally make sure the laws for your area don’t have rent control stipulations or unforeseen tax liabilities.Screen your tenants.

2) To avoid some kind of liability for unforeseen issues with the property?

Taking into consideration @Davidgreen book, Buying long-distance real estate investment. ( You kind of have to buy sight unseen) .Do you have a formula that will cover potential errors or unforeseen circumstances? 

Do budget to get a good reserve in your account for any unforeseen expenses. 

There were three lessons learned. (1) Plan for unforeseen problems during the rehab.

Due to unforeseen circumstances discovered by the lender, I as the buyer had to ask the sellers to extend our closing date to the following week from 11/15 to 11/22.

But I do use my inspection report to negotiate a lower sales price, if unforeseen problems are found.Case in point.