sureties

Caveat

If the defendant fails to appear at the hearing, the sum of money that the surety has either paid or promised to pay is forfeited to the crown.

A surety is a person who guarantees that the defendant will abide by the bail undertaking.
Every surety must:

be at least 18 years of age;
have no conviction for an indictable offence;
not be detained subject to the Mental Health Act 2000;
not be insolvent;
not be charged or likely to be charged with an offence;
be worth more than the amount of bail in real or personal property; and
not be a person for whom a guardian or administrator has been appointed under the Guardianship and Administration Act 2000.

The surety must sign an affidavit of justification before a JP before becoming a party to the bail undertaking. There is a standard form for this procedure which you should read carefully. It is a sworn or affirmed document, and you are permitted to ask any questions or see any evidence of ownership of property when determining a person's suitability to act as a surety.
You must be satisfied that the person wishing to be the surety meets the requirements listed above. You must also be satisfied that if the surety is forfeited, the loss of money is not ruinous or injurious to the person or their family.
If cash money is deposited as part of the bail undertaking, you should also be satisfied as to the origin of the money, as it may be the proceeds of a robbery and therefore have no value as to the surety.
You should also take into account the surety's character and their relationship with the defendant.

The Duties of Justices of the Peace (Qualified) Handbook, Queensland Government - June 2017, 6.4/1, 6.5/3, 6.6/1