Re: tankless hot water heaters
As long as the instant water heater is UL listed you should be good. You should be looking at an electric unit, espically if this is for hand washing only. If there is a shower, the unit needs more water than what you called for. Electric is easier to instal than a gas line.
Next, the brand. Look up your local plumbing supply store. And i don't mean Home Depot or Lowe's. I mean like a Ferguson or whatever is in your area. The unit price might be $10-20 more but the quality and support will be 10-20% better. This is what they do.
Process of elimination. Good luck.