Key dates:
June 20th - Draft. The Pistons draft 15th.
June 30th - Rosters frozen. All team/player options must be decided by this time.
July 1st - Free agency starts
July 3rd - Summer league starts. Really not sure on this one, just know it is around this time.
Some salary sites:
https://www.basketball-reference.com/contracts/
http://www.shamsports.com/capulator
https://hoopshype.com/salaries/
The salary cap wont be set until after July 1st. But they are currently projecting it at $109M with the luxury tax at $132M. With current cap holds the Pistons are actually over the luxury tax. If they renounce all FA's I think they will be about $13M under the luxury tax.
Pistons will have the MLE and BAE to spend this year.
Free agents for all teams:
http://www.espn.com/nba/story/_/id/20229609/nba-free-agent-2019-2020-team-team-lists
Pistons 2019 free agents:
Ish Smith
Jose Calderon
Zaza Pachulia
Glenn Robinson II (Team)
Isaiah Whitehead (Restricted)
Kalin Lucas (Restricted)
Wayne Ellington