Diagnosed but no insurance.

Available help will depend on (1) What state you live in (financial aid regs are state-controlled) and (2) what your income and assets are. There is no one-size-fits-all solution, unfortunately.

Hopefully you aren't in the "fall between the cracks" situation, which is that you have no medical insurance, don't make enough money to afford to buy an individual policy but make more than the allowed maximum (which is laughably low), and/or have too many assets (any money in a savings account, CD,  IRA, 401K, stocks, anything at all that's possible to access as or to sell for cash) to qualify for any of the state, federal, or private-entity assistance programs. In blunt terms, when someone literally isn't poor enough. Those various assistance programs will make you bare every penny of your personal and financial life to them without mercy and then quite possibly tell you they can't help you because (for example) your income is low enough to qualify but you have more than the maximum of $25,000 in "resources", which means that the amount of money in your personal IRA plus the 401K from your last job, plus the market value of your 3-year-old car, plus whatever you've managed to scrimp out of every paycheck to put into a savings account, totals more than that. What they're really saying is "Come back when you're three steps from living in a box on the street corner, then we can help you."  In two words: It sucks.

If you're unlucky enough to fall into that grey area, the only option is to do your own negotiating from the beginning. Tell each doctor up front that you have no insurance and cannot afford to both pay for treatment AND obtain health insurance which will probably not cover your cancer due to it being pre-existing and either denied outright or subject to a 12-month waiting period (this is where the "state of residence" insurance laws are a factor) which will help you not at all right now when you need it. Ask them what their fee for the surgery, biopsy, etc etc will be. Figure out what you can afford to pay in full and what you'd need to ask for a payment plan for. Again, in each state the laws differ as to whether a doctor or hospital MUST give you a payment plan or whether they can refuse. Ask how much something will cost (appointment, biopsy, pathology, test, surgery, hospital fees for hours in the OR, room rate, medications, chemo, etc etc etc) before doing it. Comparison shop between radiologists for mammo, MRI, MUGA scan or echo if you need them. There is a HUGE price difference from one provider to another, and on top of that, some will give a discount to self-pay patients and some will not (but most will do so; the only difference is how much of a discount -- mine ranged from a low of 20% to a high of more than 75%, and you will not know until you ask).

As far as chemo goes, your best bet is to find out what chemo drugs you will need and apply to (or have your oncologist apply to) the manufacturer for financial assistance. If you are HER2+ you will need Herceptin, made by Genentech. Genentech has a Patient Assist program that is wonderful and if your household income is less than $100,000/year you qualify under the income guideline; the other part of the application is your breast cancer medical case file which has to be submitted by your oncologist. But with the sky-high cost of Herceptin it is the only way to go for someone with no insurance.

Generic drugs (such as Taxol) don't have manufacturer-assistance programs, and so your best bet is to see if you can work a deal with your oncologist as to how much you will need to pay for those. Things like Decadron are really cheap (as in, $3 for a 20-min IV bag). Things like Aloxi (branded, no generic) can range from $400 to $800 per dose depending on what the individual oncologist charges; ask first, then shop around.

If you have chemo choices, be aware of the cost of side-effect medications. For instance, if your cancer is likely to respond equally to either taxane (Taxol or Taxotere), be knowledgeable that if you get Taxotere it is likely to lower your whitecell count to the point where you may well need to get a Neulasta shot from time to time. The self-pay cost of a Neulasta shot can vary from $3000 to $6000, depending on the oncologist. If you end up needing 3 shots of Neulasta, ouch (and I don't mean only the shot!). On the other hand, the vast majority of patients getting Taxol do not need to get Neulasta because their whitecell counts don't drop as much as they do from Taxotere. This is only one example; there are many, and the first step is to find out what you will need and what all of the options are, and of course, what each option will cost.

The no-insurance nightmare is something that nobody in our situation needs at a time like this, but there are ways to approach it depending on what your financial starting point is, and where you're located.

There is one good point to being uninsured and that is that you will have 100% control over your treatment and doctor options within your financial capability. You will not, for instance, have chosen a surgeon you really like who is in-network for your current insurance carrier only to find out that the oncologist you really want to use doesn't accept that insurance and thus you have to choose which of the two is more important to your peace of mind -- and switch carriers if you have to -- and then settle for your "second best" option for the other doctor.   The same goes for your treatment options; there will be no pencil-pushing twerp behind a desk telling your onc's office that "in the company's opinion" you should not have Chemo Drug X (which is the one you feel most comfortable with getting) for one reason or another, and thus they will only agree to pay for you to get Chemo Drug Y (which scares the pants off you). But the price - literally - of medical freedom of choice is higher and it does take a lot of time to ferret out the best ways to keep that price manageable if possible.

Edited to add: So sorry, I re-read yours and noticed that you are asking on behalf of someone else, not for yourself. However, rather than go back and rewrite the entire thing as if addressing a third person, please just read the "you" as a "general you", meaning anyone who is in that situation.