Since vacancies, late payers, vandalism and crime all come up at predictable intervals but not necessarily hyper specific locations (i.e., we know to expect Arson and Drive By Shootings in a certain area, but cannot predict 123 Main St vs 125 Main St), buying a multi-family (especially as many as 18 units) puts all of your eggs in one basket.

Thinking each "booking" as some random time interval payout.

The time of the notice must be at least as long as the interval between the time rent is due or three months, whichever is less.This may be easier to ready by looking at the MN AG Landlord tenant handbook page 23 https://www.ag.state.mn.us/brochures/pubLandlordTe...

Example:You owe $100k on your home and you have a fixed 30 year mortgage.The home is worth $200k so you take out a $50k HELOC.A HELOC is an open ended loan in which you can borrow from and payback through as many intervals as you like so long as you at least pay the minimum amount due once each month.Your first mortgage is due on the 1st of each month but not past due until after the 16th.

Not only that, they also generate new ones and store the passwords at certain intervals or time of your choosing.

Normally the initial term of the lease sets the rate for whatever period of time.Once you are past the initial period, you can provide notice of an increase with the advance notice interval for giving notice as stated in the lease. 

In terms of intervals for changing them, that depends not so much on the type of filter, but on your climate.  

We have to give them 3 days' notice, so I schedule a 2.5 hour window at a time convenient to me, then l offer appointments at 15 minute intervals during the first 2 hours.  

If you live in Texas, for you landlords that do, you can actually see how much energy your houses are using, down to 15 minute intervals by going to the website provided.

I haven't used their SEO service only because they make it pretty simple to set that up yourself and offer content packs of SEO optimized articles that you can purchase and schedule to post on your blog at regular intervals.