The tankless I installed is a Fastar that cost me less than $90.00.
Search here for Fastar, Tankless and you will get a fair number of results
The unit provided hot water pretty quickly , limited by the flow time in the line from the heater.
Run smaller hot water lines for quicker heat or mount closer to the point of use.
I fabricated the stainless steel box with a Lexan front for weather protection