I am glad to hear that you have spoken with a lawyer about your situation, although these questions, as well would best be addressed to an attorney who has reviewed your entire set of circumstances. I assume that a detailed analysis was done before advising you that marriage to a citizen was the only viable immigration option (and 245i eligibility was ruled out, as was a late asylum claim).
Further, I assume that you were told that this is only an option if you were planning to marry someone anyway who happens to be a citizen. Marrying only for immigration purposes is not only illegal, but it almost never works. So, I gather that you are already in a relationship with a citizen and were considering marriage before receiving this advice - if not, I would strongly advise you NOT to marry just for purposes of getting the green card.
I am also assuming that, if you were told by a lawyer that this was possible, that you entered the U.S. legally ("with inspection") and can prove this with your I-94 card issued upon entry.
Processing time depends on interview backlog where you live, but seems to be running roughly five to eight months (six months being about the norm) in most places right now from time of filing to interview. The Employment Authorization generally takes ten to twelve weeks from time of filing.
If you are already in community college now and they haven't asked for any kind of verification, the filing of the Adjustment of Status case is unlikely to change anything. If you are seeking to transfer and are being asked for evidence of status, you should discuss with the foreign student office of the school to which you are applying whether the Receipt Notice for the I-485, once received, is adequate evidence of status for them. It will not, though, let you switch to a student visa in the mean time.
The Employment Authorization, once received, will allow you to work.
With regard to income, generally there is a baseline annual income she should meet as a sponsor when submitting the affidavit of support form - 125% of the federal poverty line standard for a household of your size (her plus the person sponsored - you - plus anyone else she supports). Assuming that your "household" is just the two of you, this is only $17,500 in annual income.
Income that can't be proven to reach the required level may still be supplemented by showing any additional assets.such as real estate, stocks/bonds, cash-value life insurance, etc. There is no firm number value, but USCIS looks at all the circumstances - assets, future earning capacity, etc. Many of my clients are foreign students just coming out of a degree program, with no income the last few years but with assets they can use to supplement income. Plus, presenting additional assets lets us present the strongest case possible, at least in terms of the financial aspect.
If she doesn't make 17,500 and doesn't have any additional assets, your income can be used to supplement (I usually avoid doing this) OR some other U.S. citizen or permanent resident living in the U.S. and who meets the required income levels can submit a joint Affidavit of Support - often a family member such as your mother or an in-law will do this.
Hope this helps.
You need to seek immigration legal counsel at once. Based on the information that you provided, you are currently in the United States illegally. Do not delay. The questions you asked, should not be answered in a public forum. Do not talk to anyone about your status other than a lawyer.
Make sure it is a "real" marriage and not one for convenience. The CIS will be on the lookout for convenience marriages. Please feel free to visit our website for information about marriage to a U.S. Citizen in order to pursue such a case. When the case is filed you would have to wait about 90 days to have a work authorization card which you can use to get a social security number and a driver's license. Because you were told that marriage would be able to get you status, we are going to assume that you entered the U.S. "inspected". If you did not(and you do not have a 245(i) case then you may be out of luck. As you can see, the response to your query, of course, requires a deeper analysis.