I own a flat roof quadplex which consists of two single-level duplexes side by side located in Jacksonville, FL. 

Common practise is pay it yourself and bake it into rent.2.

Flat fee listing on MLS with a 3% buyer commission if you're not at the scale to get a dedicated agent who works full time for you. 

So, most landlords will pay those and include them in the rent or possibly bill them back to the tenant if they are not flat fee.

It is flat, variable, sliding scale?

I was definitely not cut out for MLM but it was very interesting to see how some people just crushed it and others fell flat.

If you were to ask an appraiser, they would value these at a flat rate that mother-in-law/pool house/guest houses would be valued.

If the building is evaluated at a conservative 10% CAP Rate, the value of the building is increased by $45,000.We’ve found this to be more readily accepted by our residents than simply charging a flat utility fee because it gives the resident more control of their costs.

Sometimes a deal can be slightly negative because you're living there as a house hack now that is a different story because you might "know," that when you move out it will be positive or positive after you raise rents and move out (lets say its a fourplex 4 flat for Chicago folks, and 4plex for us west coasters).In this case, it might be lucrative because in this example you control the "move/out," and conversion from negative cashflow to a positive cashflow scenario so the future potential is definitive versus some hope and prayer that you will someday cashflow (smoking hopeium so to speak).I've also seen some buy negatively cashflow properties here in Seattle PNW (pacific northwest) areas even after they move out (its still negatively cashflowing), but the aim was to build ADU or accessory dewelling units in the back and that eventual exit strategy would yield positive cashflow eventually.

A few years back my boyfriend and I signed a one year contract to rent a flat in Vaughan.