Home Network :: Best Option For Networking Two Computers With Only Hotspot?

I am working with a friend who has a home office that is not in a location where DSL or Cable is available. His only option for internet is using a hotspot - in this case, the Elevate Hot Spot from AT&T.

He needs to network two computers so that he can enable QuickBooks Pro in multi user mode - i.e., data file shared on Computer A, accessed by Computer B.

I thought at first that perhaps I could just setup a wireless connection for the office network - however, whenever that connection is on, then obviously neither computer can access the hotspot.

Trying to keep this at *minimal* cost.

My best idea is to old school network - i.e., connect the two computers via crossover ethernet. Am I correct that this will work? Seems to me that then both computers *should* still be able to access the hotspot via their wifi, yet also be networked for file sharing.

My questions are:

1.) Is this a correct assessment?

2.) Are there any road blocks I should be thinking about?

3.) Any reason not to do a direct connection (i.e., any reason I should entertain connecting to a switch instead?)

4.) Is there a certain order I should do things?