You can buy add on toilet seats with bidet functionality for a couple hundred dollars and they are easy to install. If you can turn a wrench, you can install one. As long as you keep the old seat to put it back on when you move out, you can do it in an apartment even and not risk penalty on move out. I highly recommend everyone get one. The brand I have is BioBidet, but I’m sure most are comparable.
You can't easily install the nice washlets in many places, because they require power to operate. If a bathroom wasn't designed for it, it's very likely to not have a power outlet near the toilet. In Japanese bathrooms, there's an outlet right next to the toilet just for the washlet. In my American bathroom in my condo built around 15 years ago, the only outlet is on the other side of the sink (meant for plugging in an electric razor or hairdryer), so you'd have to run an electric cord literally across the sink, which obviously is a no-go.
