promise of sale

If I am the seller of a house and the buyer does not want to follow the North American system which is a written purchase and sales agreement . But instead he wants to write up a writen "promise of sale" ( in spanish memorando de intencion de compraventa") which is prepared by notary and signed by both parties with a small deposit ( 5%) of sales price.
Does this memorando de intencion de compraventa protect the seller. ??? or with other words are there any negatives sides to this for the seller

thank you,
question?? is a " memorando de intencion de compraventa " with details the same as a " promesa de venta"??
in case there will be a "promesa the venta " made up with notar do you need a "memorando de intencion de compraventa "venta with notar?? it looks to me it is double work. ?
Thank a lot for all help:bunny