Praise be to Allaah.
There is nothing wrong with renting a known amount of space
on Internet servers, then dividing it up and renting it out to website
owners for an annual or monthly fee.
As for renting unlimited space, that is not valid, because
the condition of rental contracts and sales is that it should be known what
the thing is that is being rented or purchased. Not knowing constitutes
ambiguity and risk, each of which may lead to disputes. Hence sharee‘ah does
not permit that.
Muslim (1513) narrated that Abu Hurayrah said: The Messenger
of Allah (blessings and peace of Allah be upon him) forbade transactions
Ambiguity means not knowing what is being bought or rented,
and taking risks, which leads to disputes.
In al-Mawsoo‘ah al-Fiqhiyyah (30/224) it says: it is
stipulated that the object of the contract should be defined and known to
both parties, so that there are no unknown elements that could lead to
dispute and ambiguity. Having knowledge of the object of the contract and
distinguishing it from other things is achieved by seeing it or part of it
at the time of the contract, or by describing it in such a way that explains
exactly what it is, or by pointing at it. This condition is unanimously
agreed upon among the fuqaha’ with regard to contracts of buying and selling
in general. So it is not permissible to sell “a sheep in the flock (without
identifying a particular sheep)” for example, or to rent out “one of these
two houses”. That is because not knowing what the object of the contract is
leads to ambiguity and disputes. With regard to this matter, some fuqaha’
differentiated between having no knowledge of the object of the transaction,
which is what leads to disputes, and having no knowledge about a little of
the object of the transaction, which does not lead to disputes. So they
forbade the former and permitted the latter. End quote.
And Allah knows best.