It is impossible to forecast the likely sentence from the details you give.
As far as the immediate problem of the bail application goes, defendants have the right to unconditional bail unless the judge or magistrates have reason to believe that he will (a) Fail to return to court on the date as ordered; (b) Commit further offences; or (c) Interfere with the judicial process (in particular interfere with witnesses).
Your brother-in-law has been charged with another similar offence whilst still on bail. At the first hearing for the new offence Magistrates will not be concerned with his possible guilt or innocence of either of the offences. They are unlikely to release your brother-in-law on unconditional bail. They may consider conditional bail if they can satisfy themselves that any conditions they might impose will prevent or at least substantially lessen the risk of him committing further offences. (For example, if the offences were committed at night they might impose a curfew to keep him in when he is prone to get into trouble). If they cannot be satisfied that conditions will lessen the risk they will remand him in custody.
An offer of a security or surety (a pledge of a sum of money) would not be appropriate to secure bail in this case and is unlikely to be considered.