In most newer homes, the furnace and air conditioner are sized to include a finished basement. Those in older homes are generally up to the task, too, although you may need some supplemental heat. Codes require that certain amounts of air be provided for each room and for the safe operation of the furnace.You can figure out for yourself what is needed.
While the contractor is there, ask for suggestions on the best way to lay out the supply ducts and return air required by code. You may also want to ask the contractor for a bid to do the work, which isn’t always the most enjoyable task in a project.
The electrical-service panel in newer homes is usually adequate for a basement remodel. An older home may need a new higher-amperage panel to service the additional demands of a remodel. In general, if your panel has fuses, you’ll need to upgrade your service and replace the panel with a circuit-breaker panel.
If yours is already a circuit-breaker panel, see if there are enough blank knockouts below the installed circuit breakers to accommodate the new circuits you plan. Call in an electrician if you are unsure of what your panel will accommodate.