My opinion:A C corp is definitely more appropriate for an enterprise level company with multiple shareholders, executives, a board of directors, etc...

Recently flipped one of them for a nice profit and began looking for the next.

Request from the seller their Profit & Loss Statement from the last 12 months and the rent roll.Then, you can see the current income/expenses to know what current profit it makes.Then, you need to look at what the cap rates are in the area based on comp propertiesOnce you find that out, Take the profit/net operating income and divide it by the cap rate.So say it makes $20,000 profit and the cap rates in the area are 6%$20,000 / 6%  = $333k (value of building and your offer price)There are a few more factors but that should provide you with enough info on how to find the value of the building

A PM in the vacation rental can cost you 30% of gross profits.

Is it that rare to find a multifamily that is in decent condition and decently priced to turn a profit? 

Maybe- if the residency happened first then yes up to the limits of $250k profit for a single taxpayer and $500k I’d married.  

Do we just forfeit up $200/mo to him or do we get to take out expenses and then give the investor 20% of monthly profits?

I'd buy it.2%: It's a bit under at (1.48%) so maybe you're paying a bit more for the property / current rents don't justify the asking price.50% Rule: 259/unit profit is pretty good.What's your hesitation?

Using an agent to sell Profit approx 24k

Expected turn around time for return (investment + 50% net profit) is 12 months.