First you need to figure out what size of tankless water heater, because they need to be right capacity for your home, They have gotten cheaper over the last few years, as they are becoming more common, and the cost of the unit and installation will help you determine if it is worth it to you

I found the info on this site to be faulty as it suggests turning the water heater to 120 deg. F
That would form bacteria in the tank. It should be set higher with an anti-scald valve installed
Also the newer tankless are 83-94% eff compared to a standard water heater at 60%.