Our STR is on the larger side and accommodates 16 with 2 kitchens and is divided to suit 3 families comfortably.

My accommodation is paid for by the school I work at, so I could help cover fees each month if it is not all covered by the tenants rent.Any advice would be greatly appreciated.

I burned myself time after time being accommodating to people in need. 

I have seen contracts get renegotiated due to the adjustment where everyone is satisfied and can accommodate. 

Utilizing a shorter or longer lease to accommodate this can be beneficial.New lease preparation & lease renewal fees help compensate for your time or cover subscriptions for electronic signatures.

You can't afford the extra cost of accommodating someone else's bizarre payment schedule and it sets a bad precedent. 

I guess I'm being too concerned about trying to accommodate every type of tenant to fill that vacation as opposed to finding a tenant comfortable with the current amenities (i.e., no washer/dryer connections and no washer/dryer onsite).

They should let you know whether or not the specific parcel can accommodate four units.

Go find an agent who is accommodating to your schedule and stick with them, or spend a week or two and go get your license so you can do it yourself.

The City even offers up pre-approved plans (https://www.sandiegocounty.gov...) and they offer special accommodations regarding parking requirements, set backs, etc. when you're adding housing.