Some Lenders do take issue with "gift funds" or other liquidity provided by partners who are not on the Operating Agreement.

Love to partner on a flip with ya soon. 

My partner and I are currently hold 2 properties in the Glendale area that have done quite well.

Partner in other people's deals.   

One of my partners is already invested in Alabama!.

It may also cause issues if the LLC has partners not involved in the personally owned property.

I bought a building with a partner several years ago.

Also, if you go in with partners is disperses time, costs, etc. 

With rehabs you can get to significantly lower purchase prices and typically the lender will just be looking for  a100k+ ARV so that you can refinance out of the loan once rehab is completed (100k as-is value is pretty standard for DSCR loans).With rehabs experience is the biggest factor to LTV and rate so partnering up with someone for the first one or first 3 will get you significantly better terms (working in the same area can also provide benefits in terms of LTV).

Also, the state of formation is likely where internal disputes would be brought among LLC members, so if you and a partner and/or spouse live in CA, you probably want to arbitrate in CA if the two of you had a disagreement.