How do loans against 401k / 403b accounts work?

What percentage of your 403 B can you borrow?

50%

In order to qualify for a 403(b) loan, you must meet certain criteria: The maximum loan amount is 50% of your vested account balance or $50,000, whichever is less. Generally you must repay a plan loan within five years and make repayments at least quarterly.

How long do I have to pay back a 401k loan?

five years

How long do you have to repay a 401(k) loan? Generally, you have up to five years to repay a 401(k) loan, although the term may be up to 25 years if you’re using the money to buy your principal residence.