How Long Do I Need to Work Before I Can Get a Mortgage with a Guarantor?

mortgage

I’m guessing I need to have been working for quite a while to get a mortgage? I’ve just finished 6th form and I’ve never worked before so I have like no work history so far but I’m just after a rough thought how long I need to have been working before I won’t get laughed out of a bank! And will this time be reduced if I get my dad to be guarantor?