My husband and I have 3 rentals all out of state that are managed by a PM.

You've got to identify the resources you need to achieve the goal before you can determine the platform offering those resources.  

Rate will be lower with a higher down payment, so you'll cash flow more, but look at what you're saving by using that as a down payment vs. what you'd gain by putting less down and and using that towards the next property. 

And, as Nathan noted, you are likely giving up huge appreciation potential, which will likely never be replaced by cash flow.But at the end of the day, if you are in a declining market in LA and are able to find great deals in higher cash flow areas, taking into account the likelihood of needing to outsource everything and additional travel costs to visit the properties a couple times per year, and you don't really care about appreciation, then it could work for you.  

I have 10 units that are currently managed by property management.

So, I tried to help the situation by getting a contractor to go replace the floor and remodel the bathroom so that the house is nicer for her.

Downside is bad tenants, depreciating trailer if you don’t own the land, and restrictions if the park if the owned by someone else.

You can't run a business before it's a business and by saying you are setting all of these things up in advance means you don't have a good handle on the asset.

Good enough for high class properties if done by someone that knows what they are doing.  

Are you wholesaling actual "mobile" homes that are sitting on a lot owned by someone else or that needs to be moved after sale?