For informational purposes only, here is a sampling of Ethical Considerations under the New York Code of Professional Responsibility which may or may not be applicable. Ultimately, it would appear that the bidding on the property by the seller's attorney may be a conflict if it would interfere with that relationship by causing the attorney to make his judgment less protective of the client. Arguably, one may suggest that the attorney is now in a conflict situation because he has a personal stake in the ultimate sale which places his own interest above his client's interests.
However, that conflict would be between the attorney and the seller and may be waived by the seller after full disclosure. It would be preferable for the attorney to withdraw from any further representation of the seller in this transaction and be placed in the sole role of bidder on the property. This would enable the seller to retain an objective attorney to offer advice on the advantages/disadvantages of each bid and proposed contract.
These sections are taken from the New York Judiciary Law
EC 5-2
A lawyer should not accept proffered employment if the lawyer's personal interests or desires will, or there is a reasonable probability that they will, affect adversely the advice to be given or services to be rendered the prospective client. After accepting employment, a lawyer carefully should refrain from acquiring a property right or assuming a position that would tend to make his or her judgment less protective of the interests of the client.
EC 5-3
The self-interest of a lawyer resulting from ownership of property in which the client also has an interest or which may affect property of the client may interfere with the exercise of free judgment on behalf of the client. If such interference would occur with respect to a prospective client, a lawyer should decline proffered employment. After accepting employment, a lawyer should not acquire property rights that would adversely affect the lawyer's professional judgment in the representation of the client. Even if the property interests of a lawyer do not presently interfere with the exercise of independent judgment, but the likelihood of interference can be reasonably foreseen by the lawyer, the lawyer should explain the situation to the client and should decline employment or withdraw unless after full disclosure the client consents, preferably in writing, to the continuance of the relationship. A lawyer should not seek to persuade a client to permit the lawyer to invest in an undertaking of the client nor make improper use of a professional relationship to influence the client to invest in an enterprise in which the lawyer is interested.
DISCLAIMER: The foregoing is not intended to be specific legal advice to be acted upon by any person for their unique situation. It is offered as a general information discussion only. The person/persons involved are encouraged to seek local counsel in their area as laws vary from jurisdiction to jurisdiction.