i created two tables (namely: "table user1" and "table properties") with a one-to-many relationship, respectively. if i want to add two other tables namely "table user2" and "table user3", will it create a problem if i'll also connect it to "table properties" having the same quality with the former?

why would you want to have a table for each user ?

As Bob has suggested, you should not have more than one user table. If the properties table contains properties that refer to the users, then you would have a field in the properties table for userid and create a relationship between the user primary key and the properties user id field.

Glenn