You can stack your personal 50%s up for separate ventures while still knocking out deals without your own capital2) Read Raising Private Capital by Matt Faircloth3) One LLC with the S Corp designation to pay yourself a reasonable salary from the flip profits.

They barely lasted in California (they are based on London).The challenge is (1) you are assuming all listings have open houses and (2) there are a lot of moving parts that can happen behind the scenes.

How long do they sit on the market, are you finding them in move-in-ready condition, or will they need work before you move in? 

Repair the drywall and move on

I have a situation where a person I know is moving out of the country and would be looking to put their home for sale in the summer.

You need to be very committed to this if you move forward.

Them physically moving out doesn't end the lease.

Moving into the property during this time could disqualify the exchange.

The current owner listed last years income as $51,000, but currently has rents at (for the five separate units): $650, $750, $800, $825, $1125 (the math doesn't totally add up so maybe he changed a rent payment at some point). 

Personally I'm working on a very exciting niche, but will take some time to pull together; and I'll give you more details as it moves ahead.