Should I still buy a car if the frame is a little bit damaged?

I came across a really good deal on 2009 Honda civic and the guy wants 5500 for it. It has 100,000 km on it. Everything is in reay great shape but he doesn't have it safetied because there's a tiny crack in the frame in the front. Under the fan. My friend is a welder and says he can fix that for me no problem and I'll be able to get it safetied. But I know a lot of people say If a car has frame damage you should stay away from it. I was hoping I could get some insight from you guys. Is it a stupid idea and why? Or could this work and why? It seems like to good a deal to pass up!

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