you rent a flat or apartment with friends you usualy have
to sign a tenancy agreement. This
is usually for six or twelve months, but it can be shorter.
It is a legal document which sets out the dates when the rental
begins and ends, the amount of rent and the conditions. You
usually also have to pay a bond
which is equal to four weeks rent.
move into an existing sharehouse, your sharemates will probably
ask you to pay a share of the bond, but you might not have
a formal agreement like a tenancy agreement.