The margins are tough to make work.

I know there are a lot of variables depending on salary expectations, and profits per flip, but I can say that based on our past profit margins we will likely be able to recoup the cost of hiring that GC with the profits of one flip.2-hire a less experienced hourly worker to occasionally assist my husband on the same property. 

or do you look at it as, $1000 CF (margin)/month over either total ASSET price or EQUITY?

D  10% and above although the numbers look good that's if you can actually collect rent over a sustained period of time. rental properties are a very nice slow growth to add to your long term portfolio .to make big money in the business you have to be in the business IE you are the turn key provider.. or your a developer or big margin flipper etc.. rental income is rental income.. and its just long term... let your tenants pay your house off sort of thing.. 

If you only have a 5% margin closing costs could eat that up depending on the price point.

Everyone wants a lipstick flip which is non existent nowadays unless you're willing to take razor thin margins or make some kind of appreciation play. 

But is it reasonable to be worried that big companies like this will squeeze us out with razor thin margins?

This is hardly an unsolvable problemonly real downside is the market upswing that makes rates higher, creates more competition, prices are going up, and margins are getting tighter.

I thought was that it would be quick and straight forward with a small margin so why not go for it.  

Margins in many markets are getting far to thin.