Is there any prohibition in preparing the ground floor of a house as a commercial gym for weightlifting, and does the ruling differ if the owner of the project is a student of Islamic knowledge?

There is no harm in practicing physical and mental sports and opening a club for them, provided that the Sharia-compliant regulations regarding dress and avoidance of mixing (of genders) are observed. These places can be utilized for calling to Allah and spreading benefit. The fact that its owner is a student of Islamic knowledge obligates him to adhere to the Sharia-compliant regulations in his club.