Don't stay around with Buyer who request NO Security Deposit

1, Husband is real estate licensee and wife even ask no SD
2, psychology theory of foot in the door tell landlady that one Circle broad enough 1st, then middle size circle OK, FINALLY even irrational will work
3, 30 minutes afterward still unwilling to disclose offer's price (intend to drop no matter how much and deny) so politely I start with $300 but pushed to $200 [back off]
4, creditability is the key of success [still and don't follow the bad]