Beyond that, there is very little to worry about in terms of "off hours" emergencies so long as you are proactive with maintenance. 

Some of our Tennessee cleaning and maintenance teams have been impacted as they live in Cocke County which Collin H. mentioned above has been devastated by floods and knocking out their water system.

I include written instructions for payment, reporting maintenance, and how the tenant can communicate with me.

They generally have large portfolios allowing for in house maintenance and management staff along with a point person who is communicating with the local housing authority on a regular basis and has the ability to streamline operations. 

You will be spending that or more in website hosting, design, maintenance, and processing.

I would also set a maintenance/capex budget but will vary by property age and condition.

If the one lender won’t, the next one will just wake sure there is no deferred maintenance.

Are you finding the deal, are you managing the deal (filling the units, taking care of the maintenance calls, making sure rent is collected), are you funding the deal or going 50/50 on profits and losses. 

Get as long of a mortgage as possible (eg 25-30 year mortgage) to make your payments lower.If you are buying to rent it and won't be living in it, you need 20% for a down payment.Either way, you also need money set aside for closing costs, inspections, repairs and maintenance...and if you are renting it out to cover vacancies.

This can work even if you receive the net income the following month (which is normal for some PMs) What I do for my clients is record the rental income the day is earned let say October 1 and then record any expenses when they are billed even if they have not be paid yet example Hvac maintenance billed Oct 2.