I don't have access to one yet but here are the downsides. I'm not fully decided, I'll likely do SN but it's good to have options. My preferences are for a method I could ingest/swallow such as sodium nitrite since swallowing is a lot easier than any of the other mentioned violent options. I think tricking myself with something I could ingest would be easier. I would also prefer the security of doing a method in a hotel, but the failed attempt I had basically makes it so that won't be happening.
Sodium nitrite -- hospitalized, likely won't feel good physically even if there's no long term downsides. A massive medical bill because I'm American, and being otherwise enslaved in a mental hospital. I'd just be trapped at home with another failed attempt and escalating home situation in all likely hood.
Slitting throat -- I'm aware this method isn't one people on this forum are fond of, and my consideration of it would likely see people trying to steer me away from it if I made a thread on it. However, the upsides are it is transportable, can be done on a whim, and if done properly will see you pass out in a short amount of time. The downsides are it's very bloody, seeing blood makes me feel sick. At the plasma center I have to cover the tubes so I don't see it. Downsides would be physical scarring, a very expensive medical bill, and possibly nerve problems later down the road if cutting too much.
Nembutal -- It cost nearly a thousand dollars. I don't have the ability to save this amount of money due to the only income I get from plasma, I would never be allowed to save up nearly a thousand dollars.
Drowning -- I am not massively educated on this method because it is a last resort. There is a spot I have bookmarked that is around twenty minutes away from the house, and I have a 30 pounds vest bookmarked just in case. The downside is I would have to take my mothers car and likely her phones so she couldn't call the police on me, and in such a case she'd likely just go to the neighbors despite not talking to them. I would be in a hurry to do the method and it would be semi-public considering it's a lake. I'm not educated on the long term effects of a failed drowning attempt, but I'd imagine it will depend on if you passed out in the water or were caught before you got to that point. The downsides could be avoided if I snuck out at night, but it's a 20 minute drive so it'd be a while of walking. I have never left the house when not allowed, and I had a fail attempt this year. Pretty difficult to do all things considered.
Partial -- Brain damage. My mother is always home, does not work, and neither do I. I transferred from my homeschooling upbringing to living at home jobless. I have tried to get it right with a bedsheet but no dice. All it would take is her having to get up to use the bathroom or hearing thrashing for me to end up with brain damage so that's a good thing most likely. There's a pull up bar in the basement, it's very painful on the neck and I don't trust a bedsheet. It would be suffocating because unlike a rope there's not a lot of length to it.