A conveyance or incumbrance by the owner is of no validity unless the husband and wife, if the owner is married, concur in, and sign the joint instrument. [§3165.] Any conveyance or contract, such as a mortgage, lease, assignment of contract of purchase, or any act in any manner affecting the title or right of occupancy of the homestead by either party, will be absolutely void, unless concurred in by the other. If the consent of the wife is fraudulently obtained by the husband, the conveyance or incumbrance will be valid, unless it appears that the purchaser or mortgagee had knowledge of the fraud. A mortgage given for the purchase money will be valid though given alone by the party taking the legal title. [Sidenote: Liable for taxes.] The homestead is liable for taxes accruing thereon, and if platted as hereinafter directed, is liable only for such taxes and subject to mechanics' liens for work, labor, or material, done or furnished exclusively for the improvement of the same, and the whole or a sufficient portion thereof may be sold to pay the same. [§3166.] All the taxes against the owner of the homestead become liens thereon, unless it is platted as directed by statute. [Sidenote: Liable for debts.] The homestead may be sold on execution for debts contracted prior to the purchase thereof, but it shall not in such case be sold except to supply the deficiency remaining after exhausting the other property of the debtor liable to execution. [§3167.] Debts contracted after the acquisition of the property, but before it has acquired the homestead character by actual occupancy, may be enforced against the property. A judgment upon a debt contracted prior to the purchase of the homestead, although such judgment is not rendered until after the property has acquired the homestead character, is a lien upon the homestead. [Sidenote: Debts created by written contract.] The homestead may be sold for debts created by written contract, executed by the persons having the power to convey and expressly stipulating that the homestead is liable therefor, but it shall not in such case be sold except to supply the deficiency remaining after exhausting the other property pledged for the payment of the debt in the same written contract. [§3168.] Any written contract other than a mortgage or other conveyance, will be sufficient to render the homestead liable for debts, provided it contains the necessary stipulations, and is signed by the proper parties. [Sidenote: What constitutes.]