You can get a lot of mileage (literally and figuratively) out of a used bike. I would start there.
Absolutely get to know your local bike shop. I'm pretty good friends with the guys who run the closest one to me (in Cresco), and they do good work, quickly, and I'm never down for long. As someone who tends to be hard on ****, this is a big asset. Plus, it's always fun to stop in for happy hour.
Buy the riding gear. It doesn't have to be fancy, but you will be so much more comfortable and enjoy riding so much more with a pair of bibs and either some dry fit shirts or bike jerseys. It's not the most flattering gear for a man of my build (6'1" 220-230 depending on time of year), but you will straight up enjoy what you're doing more. It's not about fashion or making a statement.
I would get pedals that allow for both clipping in and regular shoes. It's not what a racer would use, but it allows you to work up the confidence to try them, or allow you to use the road bike for getting around town.
If you dig it, more bikes will come. I've gotten to the point where 90% of the year (basically if it's warmer than 10 degrees), I will commute around town with my bike instead of a car. I have a fat bike that I use primarily for winter or gravel riding, and I've also gotten mildly obsessed with mountain biking, and have a decent mountain bike as well. I wouldn't bother with mountain biking if you don't have ample opportunity within a 30-40 mile window, however, and IIRC you're in NW IA and probably don't have that close.
Good luck, and hope it works out. Cycling (in many forms) has become my favorite source of exercise and a huge part of my social life. A lot of my friends ride, and we do a Thursday night ride on the Prairie Farmer trail all summer long. Lots of weekend rides in places like the Root River Trail in SE Minnesota, Trout Run in Decorah, or Wapsi-Great Western Line on the Mitchell/Howard County borders. It's a great way to combine a workout, have a few cold ones, and spend time with friends and family.