We have a few rentals currently are trying to figure out the best way to scale that makes sense.

I am sure it could be and every property manager and some scaling up would agree.

If you want to scale up without having a high leverage of debt, in my opinion, BRRRR is the best way to do it. - You get your cash back - you will have around 20% equity on each deal when you refiGiven that buying a distressed property and refinancing take you 6 months because of the seasoning period, It is still better than saving money each month to buy another property. 

-What is the smallest/ largest loan you make (to see if you can build a relationship and scale with this person)?

I think after a couple properties when I’ve been able to mature a little more as an investor and implement systems that really help me scale I’ll look outside of SF towards the north or even out of state.

How quickly did you scale up your investments?     

Would I just continue to buy one house at a time or would it be better to try to scale up (larger package of sfh or small multis) I work a steady job and my strategy right now is buy and hold.

That being said, I know if I want to scale I will eventually have to leverage outside funds to do so. 

You will get minimal, if any, economies of scale and operational efficiencies at the unit size you're thinking about.

The LLC will need commercial loans which have less favorable rates and conditions than the conventional loans, but it is doable and others seem to be doing it to scale up their investments.