Got receipt the next day after filing petition.
In PP receipt is usually emailed to the lawyer within hours. Check with your immigration lawyer.
2-3 days at max
Mailed and received by them: May 30th Accepted: May 31st. Got Receipt of Acceptance: June 4th (2 business days) Now I'm waiting for Result (Approval/RFE/Delial). It has been 6 business days since the acceptance.
I got receipt and approval together around 2 weeks from date of apply.