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!

Honda chassis bars, do they work?

I own a 2000 honda civic. I like to take corners a little faster than the average joe, but not insanely fast. I was wondering if these parts would make a difference and by what degree of a difference would I feel.

Front and back strut tower bars, pillar brace bar, and lower tie bar.

Would I notice a difference, these are supposed to be bolt on parts, I know sway bars would make the real difference but id have to swap some lower control arms & they're a little bit more pricier than the other bars alone, so for now I would just like to know if spending money on bolt on chassis bars would give me bang for my buck.

Can my sony xav-65 55wx4 navigation added?

My cousin just got a 2007 Honda Civic and the radio was in the car already and I noticed the sony xav-65 55wx4 disnt have navigation and i was wondering is there anyway to get navi on this radio

Best wheel locking nuts for expensive wheels?

I thought locking nuts were all same but I heard people saying get some quality ones if you got expensive wheels, what do they mean by that? Which locking nuts are best? I have 1996 Honda Civic EK4 with BBS wheels.