Real estate agent seeks real estate valuation software

As a real estate agent working in the real estate industry, I am looking for real estate valuation software for market price assessments for my company in southern Germany. The solution should support real estate appraisals.

The software should meet the following requirements:

• The software should calculate a market price valuation in an interactive manner with the user.
• After the user's contact details have been entered, the market price valuation should then be made available to the user.
• The market price valuation should be free of charge for the user.
• The software should include a flat rate so that as many valuations can be made as desired.
• Additions through software development, customizing, and open source would be welcome.

A new website with WordPress is under construction.

One software workstation is planned. Work will be done with a macOS system.