This is a plain-language summary and a starting draft. It has not been reviewed by a lawyer. Do not rely on it as legal advice. This document transfers real rights and should be read by a lawyer before either party relies on it.
When you buy the exclusive, the beat is removed from sale permanently. Nobody will be able to buy it after you.
The one thing to read twice
Leases sold before your purchase remain valid. Anyone who bought the $10 lease before you keeps their files and their permission to use the beat, and their existing releases stay up.
Buying the exclusive means the beat will not be sold to anybody from now on. It does not undo licences already granted. If that matters to you, ask before buying how many leases have been sold.
What you receive
The clean MP3, and permission to use the beat commercially without the restrictions that apply to a lease. No new licences will be issued to anyone else.
WAV masters are not currently available. They are being prepared, and will be sent to exclusive buyers at no extra cost as soon as they are — an exclusive is sold once, so this is owed to you whether or not you have to ask.
The producer retains authorship credit and their share of publishing unless separately agreed in writing.