A Peruzbal is only valid if the borrower possesses some piece of land or an object connected to land. It is valid even if the borrower does not actually own the land but possesses it through renting, or borrowing it even temporarily [during the time that the lender performs the Peruzbal]. If the borrower does not possess [land or an item attached to the ground] in any way then the lender is to acquire a piece of land to him through another person [in order for the Peruzbal to be valid]. This acquiring of land to the lender may be done even not within the presence of the lender. [The Rav or other member of the Beis Din in charge of the Peruzbal document can acquire a piece of their land to all the lenders that have signed in order for them to then acquire it to the borrower and hence validate the Peruzbal. This is one of the advantages in using a Peruzbal document over doing so orally.]
Must one verify that the borrower possesses land upon making the Peruzbal?
It is not customary to do so.
 Admur 35; Michaber 67/22-23; See Chasam Sofer Choshen Mishpat 50; Nitei Gavriel 34
 Any amount of land is valid. [Smeh 67/41]
 The reason the borrower must own land: Rashi [Gittin 37a] explains the reason the borrower must own land is because the Sages only instituted the Peruzbal for a common loan, and commonly a person will not loan money to a borrower that does not own land which the loaner can collect from. Other Mefarshim explain the reason is because the owning of land considers the debt already collected by the Beis Din. [Smeh 67/41] Based on this it is understood that one who hands the actual documents to the Beis Din is not required to have the borrower own land, as this method is Biblically valid. [See Tiferes Yaakov 11; Mishneh Halachos 2/275 brought in Nitei Gavriel 6/11]
 The above is the literal wording of Admur ibid
 Likkutei Sichos 24/316
 See Chasam Sofer Choshen Mishpat 50; Nitei Gavriel 34/8