How many ATP points, or what ATP ranking, does a player need to participate in the qualification of an ATP 250 tournament?
The rules do not seem clear on this point.
There is no minimum ATP ranking requirement to sign up for an ATP tournament. A player simply needs to be a registered ATP Player Member.
ATP Circuit Regulations - Section 1.07
- For entry into an ATP Tour or ATP Challenger Tour tournament, all players must be an ATP Player Member (”Member”) or an ATP Registered Player. Wild cards are exempt from this provision.
That being said, it's highly unlikely that a player with no ranking points would be selected as a participant over a player with any ranking points.