p i c t u r e s ?

painting doors will not fix your problem if your rooms are dark

Painting your doors will do absolutely nothing to lighten a room. Their surface area is too small to have any real effect. A single door is about 18 square feet, a 12 x 12 room with 8 foot ceilings is 672 square feet of surface. The door is 2.5% of the area of the room's surfaces. Pointless.

But if you do paint, yes, you must paint both sides, otherwise, the open door will still be dark.

Electricity is even better. Yes both side but it won;t help.

Need more electrical fixtures, or pot lights.

Post some pictures so you can get some real help

What type of coverings are on the windows?

Big bright rugs!

Change all the light bulbs to the brightest ones that are safe for your fixtures. Use LED bulbs. Remove all the curtains that aren't needed for privacy. Prune shrubs and overhanging tree branches near the windows and doors. If the chandelier has shades on each bulb, remove them.

If it is still dark, add more light fixtures.

Lighting & removing all window coverings is an option.

Is it actually dark or are people calling it dark because of the dark wood? If it's the latter,

Carpet the floors is very light neutral Cheap carpet, pull back a corner in a couple areas and say " I know there's carpet in here now but there are beautiful hardwood floors protected under here!" Then let them deal with it after they move in.

You can add your pics right here in the comment section so we can see what the buyers see.

If the house is old and the doors are stained and in good condition, I'd keep them like they are. You haven't told us about the wall colors/coverings. That may be the prob, post pics.

bright light bulbs and white shades if your shades are dark. can you bring over a few of your light fixtures for the far corners? have the windows washed and pull the window treatments all the way up. if you have central air, turn it on and take off the window screens if they are a culprit.

if your mom's house is older, and the rooms are small, etc... its a matter of the right buyer at the right price, who wants to take down walls and open things up.

I have shown homes where the doors and trim are dark and the walls are light and the home shows dark. It is generally the lights as many have pointed out above. Occasionally the buyer just doesn't want to have to go through the painting process to repaint the trim. What also contributes to that 'dark' comment is too much furniture/too cluttered. So really, without pics we can't comment on your specific rooms. Post a few for an idea of what can help you specifically.