I talked to Chase, but they don’t offer SBA loans for self-storage; they require the owner to occupy a certain percentage of the building/storage, which is not the case with self-storage.

Speak to your lender/broker for a closing costs estimate, which will be much more accurate than a percentage range. 

.- While self-managing either type of property is possible, if you hire out property management you'll pay a higher percentage for a skilled MTR manager than for someone to manage your Section 8 property.- While MTRs can be any size property, the bedroom/bathroom count is really important, especially with larger properties.

I ran number multiple times but my estimation seems not great as I am not sure what percentage I should allocate monthly expenses as the recommandation is a range such as 5%~15%.

It's possible the deal is ok, but your enjoyment percentage, even for 18 months, isn't that great in a unit like that.

Ca has the highest percentage of investor own SFH in the nation.  

Some will do it for a percentage of the first months rent.

A high percentage of them are inexperienced and just shopping by price - which is really a waste of time for a good PMC.

I learned how to calculate my yield on loans that I cashed out as an annualized return vs how much I made in dollars or percentage over what I paid.

What percentage is a good C on C return?