A pipe dream in the basement?

Finishing our basement would give us over 500 square feet of extra space for playing or movie watching or whatever. On top of that it would give us another half bath. I’m entertaining the idea with my dad very loosely since it’s an investment I’m not yet ready to make. Regardless, I’d like to know what the materials would cost since the labor would be fronted by my dad and me (mostly him since I still need to work full time and because he’s more of a master at this stuff) as well as AbC. I have a number of great memories doing home improvement projects with my family as well as going to job sites with my dad as a young boy and teenager, so I think the time is right to help AbC build some similar memories of her own.

basement-diagram