Nc for this as outing. My db and I have always been close. When he went to uni he struggled with money as he has no self discipline I.e if invited to the pub he'll just go and ask me for money for food/bills rather than say sorry I can't afford it. I always lent it to him and he always paid it back in full when his next student finance came through. Not an issue really except I would even lend it if it meant I was living on credit cards for a while, leaving myself struggling. My fault but I was trying to be a good big sister and I know what it's like to be scratching around for money.
Anyway, he's now finished uni and is working full time. Albeit in low paid work til he gets a 'proper job' (yeah he's a snob like that and thinks this job is beneath him). I was in a bind this week and couldn't pay an urgent unexpected expense (lost purse; cancelled cards). I asked him for a short loan.
He got really nasty on WhatsApp, said it was my own fault and that he didn't believe I would pay it back. He then said he didn't have it when I knew he'd been paid 4 days before. We had a huge row and he just laughed at me, called me stupid etc and said some really nasty things.
This isn't really an AIBU. I just wanted to get it down because I'm so disappointed in him. The amount I asked for was small and would have been paid back by 4th october. In the end I had to borrow from my DM who is away on holiday and use her card for the expense.
Both of us live with DM. He has agreed to pay rent but dodges it. Doesn't do any housework or cooking. Normally I pay the majority of bills so end up subsidising him as he doesn't contribute. And the final straw this morning was he's left an almighty shit in the toilet which is stinking the house out and hes gone out 
I know I can't do anything about it. It's just pretty horrible when someone you're close to and have helped out one sided a lot throws it back in your face 