Actually, I need to amend my answer too. We each have our own discretionary spending accounts. Our personal goof-off fund that we each do whatever we want with, whether it’s me buying a new bike part, or her buying… er, a new bike part.
If the loan had to come out of our money, there would some consultation involved. Mainly because that’s where our bills and household costs are covered, the fact that I’m lending money to someone is not as much a big deal (we trust each other’s judgement). But covering Larry’s month from my goof-off fund would not be something I’d have to clear with her, but if I had to do it a second time, I’d seek her counsel.
Interesting question - I’ve never thought about this before. I’m not much of a lender, either, and I consider a loan to a friend to be a bad idea, and I am also of the school of thought to not loan more than you can afford to lose (this idea has really been cemented by watching Judge Judy).
If it was a loan to a family member for something like helping them avoid losing their house, Jim and I would sit down and discuss it; I don’t think either of us would be making loans to anyone without discussing it with the other. The amount we would loan to a family member in these circumstances would depend, and we’d probably draw up paperwork on it (I am not only a tightwad but also an accounting clerk - I like concrete terms). If we went the other way and only loaned the amount that we could afford to lose, it wouldn’t be very much (a hundred or two), and we would still consult the other.
I guess the answer to the OP question is, “Not much.” 
Short of ‘covering lunch’ type loans, I do not loan anyone money.
If someone needs some cash to get them by a rough situation, anything under 500 bucks I would handle myself out of my personal savings (from my monthly allowance that I never spend all of). If it were more than that, we would have to dip into our money and I would discuss it with my husband. But this would be a gift (if they wanted to call it a loan to make them feel better, whatever, but I wouldn’t expect it back).
This is all very hypothetical, though. I can’t see this ever happening with close friends or family.
My limit on lending money to someone without talking to my husband first would be the same as my limit on spending money without talking to him first. So, nowadays, up to about $200, probably. There have been times in our marriage where that threshold was lower.