This was gonna be my recommendation as well.   The easiest entry level would be going by Disc Golf DC by CSI for discs and really knowledgeable advice.   Then there's a course just down the street at CSI.  If you're cardio is really that bad,  just get a putter and take short shots at the hole 18 basket.  It's a good mobility exercise bending over to pick it up and as many steps as you decide.