There is no "physical property" involved in the sale

all computers etc. where included in the sale agreement

Computers are physical property.

This is a sale of  business assets by the father. Both parties should agree on  the breakdown of the sales price into categories such as:

Fixed Assets

Accounts Receivable

Goodwill

Accounts payable assumed

Etc. They each complete Form 8594(?)

Then the sale of each one gets reported appropriately-Sch C, Form 4797, Sch D/8949.