Kiddushin, Chapter Two, Mishnah Nine
This mishnah lists things from which it is prohibited to derive benefit. Therefore, a man who tries to betroth a woman with one of these items has not betrothed her. In my explanation I will explain what each of these items is.
1) If he betroths [a woman] with orlah, or kilayim of the vineyard, or an ox condemned to be stoned, or the heifer whose neck is to be broken, or a lepers bird-offerings, or a nazirites hair, or the first-born of a donkey, or meat [boiled] in milk, or non-sacred meat slaughtered in the Temple court, she is not betrothed.
2) If he sells them and betroths [her] with the proceeds, she is betrothed.
Orlah: Fruit from a tree during its first three years (Leviticus 19:27).
Kilayim of the vineyard: Wheat which has been planted in a vineyard (Deuteronomy 22:19).
An ox which is to be stoned: An ox that has killed a person must be stoned to death (Exodus 21:28).
The heifer whose neck is to be broken: This refers to the ceremony performed when a body is found and its murderer is unknown (Deuteronomy 21:4).
A lepers bird-offerings: At the end of his leprosy (tzaraat) the leper brings two birds as sacrifices (Leviticus 14:4).
A nazirites hair: The nazirite cuts his hair at the end of his naziriteship and burns it (Numbers 6:18).
The first-born of a donkey: The first-born of a donkey must be redeemed by donating a sheep. Until that point it is prohibited to derive benefit from it (Exodus 13:13).
Meat [boiled] in milk: Exodus 23:19 and parallels.
Non-sacred meat slaughtered in the Temple court: It is forbidden to slaughter non-sacrificial meat in the Temple court.
Section two: It is forbidden to derive benefit from all of the above items. They also may not be sold. However, if he does sell them, the money does not retain the prohibited status of the original item. Therefore, the money is effective for betrothal. Note that the mishnah does not state that it is permitted to use the money for betrothal. The act may be prohibited but nevertheless effective.