There are some rotary flying jobs that are naturally attractive - for many HEMS is one of those. I have been fortunate enough to start helicopter flying as a second career and done various really rewarding roles including HEMS pilot. It is possible, but it will never be financially a brilliant option. Various things affect the chances of success: overall things are not good at the moment. However, being selfish you only need one job at a time.
Before you become a particular type of helicopter pilot you will need to gain experience appropriate to that work; arguably that is more difficult than getting the licences and ratings. Acquiring a licence or rating is just the start. In the main, helicopter flying is single pilot flying. A problem is that you cannot sit with Nelly and learn your trade by flying as a co-jo.
In my experience progressing in helicopter flying involves jumping a series of hurdles. You can take different routes but you normally need to jump a hurdle to get to the next stage. Immediately post-licence the first problem is how to gain any additional hours - you are virtually no use as a commercial pilot at that stage. Once you jump that hurdle you need to find a way to become a useful single engine turbine commercial pilot, then to get some twin engine experience and so on.
Be very careful about offering to fly for free. You have seen the reaction here and it is general and understandable. Also, if you are prepared to give yourself for nothing, that might be seen as implying something about how much you value yourself. However, you can usefully spend your time developing good relations with people in the industry. This might well involve spending time doing things ancillary to flying. For example, it would be useful to spend time working at ground handling at pleasure flying.
It is important to develop and keep a good reputation: the hele industry is a small one.
You will also face some difficult decisions. Helicopter flying is hazardous and in the end you need to control the risk you expose yourself to. I have felt obliged to turn down or resign from various jobs where I had serious concerns about safety. Without being too dramatic, in at least one case the pilot who took on a role that I declined is now dead. I recently turned down a job I would have loved to do, because it just did not make any financial sense.
Having means of support outside flying could be very useful. Particularly at first, you may spend a lot of time looking for flying. However, be aware that flying can be all-consuming and deflect you from other bits of your life, including your other business.
I have taken the view that I wanted to enjoy all of the flying that I do. In general, I have done that and enjoyed my early flying just as much as the more exotic stuff.