Forgive me if I don't know the archery-terminology, its been years since I've released an arrow. My primary advice is to go shoot at a local archery range if you're a beginner, and you'll probably get competent advice there as well. When I started to shoot, I didn't buy any equipment - I could get a beginner's set of everything I needed at the archery range at which I trained. Once I started going to competitions (who says your dad won't? : ) I bought my own equipment and also maintained it, but that was after 2 years of using standard rented equipment. Plus - I found the crowd at archery ranges to be quite easy going, a very pleasant surrounding to spend time.
Health: First off - the health issue. I practiced competitive archery for 3 years, and don't recall ever getting an elevated heartbeat. So circulatory problems shouldn't be a worry. Depending on the volume of arrows you shoot, or if your bow is too strong for you, you can have cramps and muscle-aches in the back/shoulder area. But if you take it easy at the beginning, and slowly work yourself up to higher volumes and a heavier bow, you should be fine.
Equipment:This is an overview, best to consult someone at the shop or better yet at an archery range, about buying equipment. The expensive stuff(bow, arrows), you'll probably be able to rent at the range for a membership fee, and is what I'd start with, until you feel you like archery enough to buy your own bow/arrows.
- Bow: there are 3 types of common bows: long-bow(stick with a string), recurve(end of sticks curve in shooting direction), compound(wheels & pimpy technology). The long-bow is generally shot for aesthetic reasons, say if you are interested in medieval times, or have a back-to-nature thingy and want to practice archery in it's "pure" form. Compounds have an initially hard draw, then the draw becomes a joke - helps to keep stable when aiming. Recurves have a fairly evenly difficult draw, and are the olympic standard for archery (I think).
- Arrow: too many types to explain, depends on the bow, the target, and how much you want to spend. Best to ask at the local archery store about each individually available arrow type. Apart from that, you want to differentiate between 3 parts of the arrow - the head, the shaft and the feathering, which can be put together in various combinations.
- Protection: when you release that string, you don't want some piece of body getting caught in its way. A MUST is a fore-arm protection, for the arm holding the bow. It's basically a leather strap which you tie around your arm. Some people, for example if you like to wear windy clothes or have a big chest(belly ;), also get breast-protection to keep the chest on the side of your bow-holding arm all packed in tight, so the string doesn't chip off a nipple. Then most archers also use a finger-thingy, which you put on the fingers you pull the string with, to protect your skin from too much wear.
- Aim: unless you're shooting long-bow, you'll probably use some sort of sights. Maybe for the first couple times holding a bow you'd shoot without.
- Stabilizers: are counter-weights on rods which get attached to your bow, so that the force of releasing the arrow doesn't shake your bow too much - which can be a pain after shooting a couple dozen of arrows. But this shouldn't be a problem with lighter bows.
Good luck to your dad. In the end, good shooting is about securely repeating form. Equipment comes second.