PS to my previous post:
An escribano might ask for and/or accept IRS form 1099 from employers that "prove" previously "earned" income, but I am not certain.
AllI know for certain is what I was told and that my bank statements and a copy of the sales ageement were enough to satisfy the escibano at the time of the escritrua (which took place ten days after I saw the apartment for the first time).