A finished basement is usually the cheapest square footage a Maryland homeowner can add. It is also the project most likely to be done badly, because the parts that matter most are invisible once the drywall is up.
Three things determine whether your basement finish is worth the money: water, egress, and ceiling height.
Solve water before anything else
Finishing over a basement that takes water is throwing money away. Before framing, the source has to be identified and corrected — regrading, downspout extensions, and gutter capacity fix most of it, and interior drainage with a sump handles what grading cannot.
Once the water is controlled, the assembly matters. Framing should stand off the foundation wall, insulation should be rigid foam or closed-cell rather than fibreglass against masonry, and the flooring should be a waterproof product. Carpet directly on a slab is a decision people regret.
Egress is not optional for a bedroom
Any basement room used as a sleeping room needs a compliant emergency escape opening — either a door to the outside or a window meeting minimum opening size and sill height, with a properly sized window well and a ladder where the well is deep.
Retrofitting an egress window means cutting the foundation wall and excavating outside. It is meaningful work, and it is far cheaper to plan for it than to add it after a failed inspection or a problem at resale.
Measure ceiling height before you plan anything
Finished ceiling height is the constraint that quietly kills basement plans. Ducts, beams, and plumbing all eat into it, and once the ceiling is furred and finished you can lose several inches from what you measured.
Where height is tight, the answers are rerouting ducts, using low-profile lighting, and boxing beams deliberately rather than dropping the whole ceiling. Occasionally the honest answer is that the basement is better as excellent storage than as marginal living space, and we will say so.
If you are planning to rent it
Montgomery County and Prince George's County both have specific requirements for accessory dwelling units and separate rental spaces — egress, ceiling height, separate entrances, smoke and CO detection, and in some cases fire separation and parking.
Building to those standards from the start costs less than retrofitting, and it is the difference between a legal rental and a space you cannot advertise. Tell your contractor at the estimate stage if renting is anywhere in your plans.