It's really too general of a question. If you've not been riding recently, you may be surprised just how hard those hills are. That doesn't mean even at 79 you can't get fitter and conquer those hills. Though likely it will be relatively more difficult compared to someone younger. Of course, I'm generalizing. I'm 64 and I don't doubt there are 79 year-olds that would leave me in their dust.

Something to consider is an ebike. Essentially an electric bike makes the hills much less steep. This doesn't mean you don't have to put in effort and you can usually adjust the amount of assist to match your requirements. So, you will still get a workout, if you want. It just may be the difference between being able to ride those hills or not.

If you're really unclear what you would want, then I'm with those suggesting getting a truly inexpensive used bike. Preferably from a bike shop that has tuned it up. That way it is actually usable. See how you get along with that and then if needed, buy the bike you really want.

When I started riding 6 years ago, I used my 25-year-old "dad" bike. I got it tuned up at the local bike shop (LBS) and had no idea what to expect. I went riding for the first time in years, just to ride. It was really hard getting just 1/4 mile up the 3% slope where I live. Like sucking wind really bad. But very quickly I got fitter and within a few months I was climbing all over the place with that bike. About 6 months in, I could see I really like cycling and bought a new bike, now knowing what I wanted.

In any case, the best of luck to you and enjoy your future rides.