I'd concur with all of the above. Building up a client portfolio takes time. You can
earn this kind of money once you're established but it doesn't happen overnight, unlike the office job where you start on Monday and get paid a month later. I think training is important, too. As is getting some experience.
I'd also add that it's worth factoring in the hidden savings. When I lived and worked full time in London, my annual tube ticket cost over three grand, and that was a few years ago. I hate to think what it costs now! I have a child so if I was office-based I'd have to pay for childcare during the holidays. Good quality childcare doesn't come cheap - nor should it - so that's another saving. There's also the issue of work clothes. This may sound trivial but in some workplaces there's a certain dress code required and that will cost you; I, on the other hand, can proofread in my PJs if I want to! I also used to spend a lot of money on lunch when I was in the office - and those little trips to Pret add up! I could go on but you get the picture - it's not just about what you earn but what you don't spend
For me there are the emotional savings, too. I like the flexibility that this kind of work allows me. Kate's point about peaks and troughs is important because sometimes these are imposed on you, but sometimes you impose them on yourself because it suits you. I take the month of August off because I want to look after my child rather than having her in various summer camps or in day care.
Being freelance is about being patient, strategic, and taking the long view as you build up your business. I would imagine these factors apply to anyone looking to become self-employed! It's also about lifestyle and individual choice. What works for me might not suit you, Kate, Curdles or Sarah. And of course it's about money, too - there's no getting away from it, especially with the economy as it is at the moment.
You may also be interested in the following article on my blog: Proofreading – Does it Pay?
There are also posts on training, starting out and getting noticed that may be of use - look in the Archives on the left-hand side bar. I'll also be posting a series of three articles on developing a business plan in a month or so. I think that anyone proposing to become self-employed needs to do this and it echoes the other comments about considering where your market is, how you're going to reach it, what skills you need to be attractive to your chosen client base etc.
One final point and then I'll shut up. If you do this you'll be building your own business. That's a hugely important cultural shift. Every step you take on the journey will be an investment in yourself. Every piece of training or work that you do will be for you and your business. Office-based part-timers (I've been one) typically put in more hours than they're paid for in order to be seen to 'keep up'. They don't always get the same breaks as full-time colleagues or have the same degree of influence within a department because they're not always on site. This is where the cultural shift happens in our line of work - I don't consider myself a part-timer; rather, I'm a freelancer. I'm not an employee; I'm self-employed. I'm not even just a proofreader - I'm also the owner of a business, the chief accountant, the marketing director, web manager, coffee maker, and the errand runner! And I'm really proud of that. Maybe you could try to explain this side of things to your husband. Like Kate, I think having the support and encouragement of a partner when you're doing something as important as setting up a business is crucial. My husband has supported, encouraged, consoled and advised me at various stages of my journey since 2005 - sometimes in the early days I couldn't see the wood for the trees and it really helped to have him there to offer an alternative perspective or just help me to chill out over a problem and come back to it in the morning.
Obviously, if the immediate financial issues outstrip all else this argument may not cut the mustard. Only you know the ins and outs of your particular situation. But if that's the case why not try Sarah's route and grow your freelance business on the side while you do office work? It would require some extra commitment but you'd not be putting all your eggs in one basket, at least!
Good luck with your journey, however you choose to proceed.