I'm in the later stages of purchasing a niche sub-contractor in the SE US. I'm now working with the sellers on the nitty gritty handover items that need to be transitioned. Here is a summary of my working list:

Insurance: (Staying with current provider)
- auto coverage on fleet of 40+ vehicles.
- General liability policy.
- Workers Comp policy.
- Bonding, done on a job by job basis, for a minority of their work. (I got a backup quote from another bonding agent for a fall back).

Benefits:
- I'm doing an asset purchase, so retirement benefits will likely have to start fresh under new entity. Will keep the same provider.
- Health Insurance will remain with incumbent, but have to migrate and re-enroll everyone under new LLC.
- Exhaustive list of emp perks.

Payroll:
- Currently done in-house, and paid weekly. Will keep the same, but need to get everything lined up based on timing of close and bank account. (See below).

Bank Accounts:
- Goal is to keep the same bank account for now, to reduce number of changes- less to go wrong. Built in a true-up with sellers for any payments post-close that shouldn't have carried over. MAKE SURE to change authorized signers.