I just want a solution that is as hands off as possible and can generate $4K a month in rental profit.I’ve been looking at properties in the UK, but they either tend to be quite expensive or generate low rents.

your job isn't to educate or provide & explain the solution on the first call. 

Keyscan, DMP, Alarm.com, Honeywell, Brivo, and others all have commercial door access system based on keyfob solutions. 

I'm in process of building a solution to help owners find property managers.

@Delicia M.Here is another solution.

And I Already replaced all the old hardware with modern brushed nickel when I bought the place 16 years ago.

@Thomas Hallowes, A partnership like @Derek Carroll mentioned might be an attractive solution. 

I wont forget how amazed one of the agents who was showing me around Atlanta was when I introduced him to Waze a few years ago, which forecast  a stopped car around the bend - and sure enough there it was :)I land up needing to call my US bank on a landline more often than I ever need to call my Iocal bank - (in fact come to think of it I never call my local bank) The solution is to find a cell package that includes foreign calls in the base price- and then you don't think twice when you need to call or for how long.

The answer really depends on your state and local laws and varies from place to place.Rather than worry about two deposits, an easier way (if you can do it) is simply collect a larger security deposit and make sure your lease includes unpaid water bills as something that can be deducted.The best solution is to have a great property and find great tenants who pay their bills.

I'm looking into a property mgmt software as a long-term solution, but its good to know I can sync up all my calendars for free in the meantime.