Sounds like someone needs a legal writer.
I would caution against having legal documents or sales contracts "checked" on an ESL board.
Of course, I'm not a moderator but in these kind of situations the buyer and seller should protect themselves by securing legal counsel or, at least, a notary. This also protects the operators of this board should anything untoward develop from the transaction wherein the document, that may have been reviewed in whole or in part on this forum, is used.
/not a lawyer, don't even play one on TV
Hope this helps.