"so they have around 20 properties they don't own"

That means there is Liability that should be passed over = the tenant prepayments and deposits against move-out or last months' rent. You would not want to treat that as an asset. Is that a net $950k goodwill? Is there cash on hand in a trust account?

"computers, office equipment and a couple vehicles valued at $50K"

That seems pretty high, unless they have lots of vehicles (more than a couple), such as for maintenance or housekeeping staff.

"buying a rental property management business"

So, a book of business? The entire entity? Or, just a customer list, really?

Do the buyers have a decent business evaluator?