Danb1,
A little caution when approaching this task will pay off well in the future.
1. Verify what permits are required and pull them. The jurisdiction that the "2 family home" is in may require an electrical contractor, that is locally licensed, bonded and insured, be the only entity to do the work. This is a local legal concern.
2. If you can pull your own permit to do the work, hire a local master electrician to come to the 2 family home and evaluate the system. An old system, such as you describe, is not a simple thing to upgrade. Be prepared to take a lot of notes because the amount of information that is involved with the common "old ******** system with a lot of subpanels" is large.
3. Set up the relationship with the local master electrician that visits the 2 family home so that you can follow up with additional questions.
4. You will almost certainly have to pay for this electrical consulting, but the pay off is that a future disaster is far less likely to occur. It is very cheap insurance.
Respectfully,
Al
