Yes you can.
Yes, you can charge your 18 year old child rent, and if your child doesn't wish to pay, he or she is free to move out and live elsewhere.
No. A 12 year old is a minor and a child. They can not enter into a contract to rent an apartment.
Yes, it is possible for your 18 year old student to rent a furnished apartment in the Dallas area. However, many schools will require freshman students to either live at home or on campus.
No rental agency will rent to a 12 year-old.
yes
Perhaps for lack of money with which to rent an apartment. There could be lots of reasons. Of course, they are not necessarily good reasons. A 31 year old should not live anywhere he or she is not wanted.
yes
It depends on the local renting agents requirements. Most require that you be 21 years of age. But you may find one that will rent to a 20 year old especially if you are married and have a good job. Rent a wreck will for the most part rent to a 20 year old.
sure. good luck getting someone to rent to you though.
Yes (assuming they can find someone who is willing to rent to them)
Yes they can.
No.