I am looking to replace my water tank with a tankless water heater. What price range should i expect to pay for install and the tankless heater itself. Also is Home depot and/or Lowe's a good deal?

My home is entirely electric no gas. I currently have the typical 50 gallon water tank.
The tankless water heater would be for the entire home - It is a 3 bedroom townhome that is 1800 sq. feet.

My reasons to get the tankless water heater are.
1. Tired of having to wait 30+ minutes between showers.
2. My current water tank takes up half of the storage closet and its in the front of the closet.
3. In the future It would help sell my townhome over another in the neighborhood as all the townhomes have a very similar floorplan and similar look.

to increase the gas pressure from 8" WC to 2PSI when converting from a gas hot water heater to gas tankless heater? Gas line is 1" entering the house, then 3/4" to each appliance. House is in Texas, 2 stories, 3200 SF, 3-1/2 baths (with a whirlpool tub), 2 furnaces, fireplace, dryer and tankless heater. If increased to 2PSI, gas pressure regulators will be needed at each appliance, as well as a 2PSI meter installed by the gas company. Sounds more expensive than necessary to this unknowing consumer. Comments are welcome.

Our ph is 7.8 -8.0 and a very high carbonate hardness. Have to replace heating elements often. Am unable to use a water softener to ease the situation. How does hard water affect the tankless heater?