If I had to take the marc train station to New Carrollton, Would I have to purchase a ticket using the machine? Does the machine accept cash? Cars on the fritz, never have used the train.

The machine at Halethorpe takes cash. Atleast that it what it says on the website and on the machine. You can always download the CharmPass App for tickets on your phone because at times the machines are out of order. If you pay with cash on the train there is a 5 dollar fee and they not accept any bills larger than a 20.

I think the machine only accepts cards

You can purchase aboard the train with cash but it's an extra $5. I recommend using the machine.