Home charging question (extension cord)

I want to buy a Tesla MYLRRD but have concerns about charging it at home. I'm in Los Angeles which has a lot of superchargers but I hear it's still a pain if I can't have a home setup. I live in a rental unit with an outdoor parking spot without EV charging. I have a 240V NEMA 6-20 outlet inside my unit that I'd use with a mobile connector. However, my parking spot is quite far so I don't think the 20ft of mobile connector would reach the charging port. I'm thinking about using an extension cord (like a 25 ft one). Is that safe? It seems like the manual advises against it but I'm seeing posts with people doing that. Would it be okay to have this be my main source of charging? What type of extension cord should I purchase?