I'll be happy to challenge your MBA idea because I recently went through this and decided in the end that it is not worth it at all. First....what do you do right now? If it's anything remotely finance or consulting related, you can get into both IBD or VC without an MBA. Have you actually tried just applying for any of the jobs you want? Maybe you can just get them at any rate, looks like you already have some work experience. I thought I could not get the job I wanted without an MBA...but then again I didn't want to waste 2 years of my life + tuition + opportunity cost of lost earnings, so I went ahead and started applying for the exact same jobs that I thought I needed an MBA for (bc most of them asked for that in the job descirption). Turns out I didn't....I got my dream job within 3 months, lol. So before you go do this, make absolutely sure that you can't get those jobs without an MBA. It will just take you a few months of applying to find out, definitely worth to put in the effort. Secondly, if the only thing you are lacking is finance skills, then go and do the CFA, much cheaper and you'll learn more than in any finance MBA class and it's globally respected. Lastly, a lot of IBD and VC jobs are based on connections...if your brother works in IBD and makes 1mn a year...then he is an MD or at least a senior VP which should equal connections....see if he can help you.
Also, be careful what you wish for, if you have never even interned in an investment bank or stepped foot into a VC firm (and yes, you should figure out which of those you actually want, they are VERY different), then make sure that you actually want to do this! Working 80 hours+ a week doesn't so bad when you talk about it....but wait until you actually have to do it.
If you do go down the MBA route, make sure you go to a top 10 school (HBS, Stanford, Wharton, INSEAD, etc.). If you do some 2nd tier MBA, then you'll probably not cut it for the IBD or VC firms unless you make some good connections....and the way I see it, you can make connections in many other ways that are way cheaper than an MBA. Just get a list of VC firms in the Bay Area (google), cold email them and ask if you could do an unpaid internship for 3 months. You'll probably get some responses and this way you get connections and you can figure out if you really want this. So my two cents are, before you go do an MBA, make sure you know EXACTLY why you want to do this and EXACTLY what you want to get out of it and what you want to do afterwards. Just because you like to study and want a break from your job (which btw is why a lot of people do an MBA) is not a good reason. You could do online study and take 6 months off, you would save a lot of money that way. And of course it's October...it doesn't hurt you to apply for an MBA for next fall and do all of the above until then....you can always still change your mind and turn it down if you get in...which is what I did. Good luck!
PS: I work in the finance industry, have done IBD and PE and have also done CFA, similar age as you, so if you want any more advice, feel free to PM me.