This. ^ When my best friend's (BF) daughter was at uni -12-13 years ago, she needed guarantors for the student house, (for year 2, she had her first year in Halls,) and my BF wouldn't do it. Because she couldn't. She was in a precarious position financially after the credit crunch, as her DH had lost his fairly well-paid job he had had for 2 decades, and had to take a lower paid one (40% less pay.) They had about £30K of debt at the time, and struggled to make ends meet.
They said no - sorry but no. The LL is going to have to trust you to pay the rent. The other 4 people in the house (her 4 mates from uni) all had their parents be guarantors. All had quite well-off parents. On much more money than my BF- and her DH... (some £80K - £90K joint income, compared to my friend and her DH who had £25K between them.)
The other parents owned land/farms/businesses/villa in Spain/small private yacht etc, and they were happy and able to be guarantors. BF couldn't. The LL was OK to let her DD be the 5th tenant without a guarantor as she was happy with 4 out of 5, and the 5 girls were firm friends and the other 4 wouldn't move in without the 5th girl. (BF DD.)
Turns out it was a wise decision as my BF's DD pissed about with her money. Got bursaries and extra monies as her parents were on low money, and spent the whole term's money in 6 weeks. By 5 months in she had only paid 2 months rent. The landlord was patient and tolerant, and waited for her to catch up - which she did. She was straight by 8 months...
But if my friend had been a guarantor, the landlord would possibly have chased her for the £1125 rent owed. (3 months.) She was on the bones of her arse at the time, and already struggling to pay mortgage, loans, overdraft fees, bills etc, and had more outgoings than income... And debt collectors chasing her for £1125 would have finished her off.
Unless you have multiple 10s of 1000s surplus income, it's incredibly foolish to be a guarantor.