The following varieties may also be noted: A condition collateral is one requiring the performance of a collateral] act having no necessary relation to the main subject of the agreement. A compen condition is one which expressly requires a thing to be done, as, that a lessee shall pay 8 specified sum of money on a certain day or his lease shall be void. Shep. Touch. 118. Concurrent conditions are those which are mutually dependent and are to be performed at the same time. Civ. Code Cal. § 1437.. A condition énherent is one annexed to the rent reserved out of the land whereof the estate is made, or rather, to the estate in the land, in respect of rent. Shep. Touch. 118.