Should i do this?
Most Helpful Girl
No, you'll end up on Judge Judy or Rinder. One lesson that's taught me - NEVER LEND A LOT OF MONEY TO A girlfriend OR boyfriend.
If she can give you the money in 3 weeks, then she should wait until then to buy the car. If she can't, then tough luck. How does she think other people manage without a boyfriend to lend them so much money?
If you're not comfortable about lending it, then don't. It's a lot of money to lose out on if anything does go wrong (and trust me, they do). I'm sure you know that relationships can change very quickly. It's up to you though.
Most Helpful Guy
"Trust is the prerequisite to deceit." - Hebrew proverb
Then she should have no problem signing a "promissory note," and having it notarized before a notary public to make the document self-authenticating. Additionally, she should have no problem with language which entitles you to all reasonable costs and attorneys' fees in enforcing the terms of the promissory note, litigating in a trial or appellate court, or enforcing a money judgment and collecting upon a money judgment.
Otherwise, good luck enforcing, and good luck collecting.