Do I need a real estate broker or an attorney?

Do I need a real estate broker or an attorney?
My husband and I own a small commercial building
with 4 store fronts. These units are now occupied with
renters that pay on a monthly basis with no written
rental agreements. My husband is retiring and we hope
to be able to live off the rent we receive from our
building. We would like to change the terms of payment
to extended leases. Our property value has increased
and we are going to be asking a significant amount
more than what we receive currently. How do we go
about informing tenants of this change and who do we
go to for advice on how to proceed with our plans? I’m
not sure if we should speak with a real estate broker, or
meet with a real estate lawyer. We really cannot afford
to be spending a great deal on advisor fees as our
money is wrapped up in this building. We have no
experience with leases and really need someone to
help us step by step to put this plan into motion. We
prefer not to sell the building at this time as I am 17
years younger than my husband and would like to
retain ownership until I am ready to sell in the future.