You should be billing a multiple of the approximate annual wage to offset the risks of freelancing. Twice is good, three times is better. If you can't do that you're much better and safer off to find employment so make sure you understand exactly what the risk/reward trade-off is for being a freelancer and set yourself up accordingly.

Find customers that value you and make sure they pay and pay on time. A single hickup in the payment department is a good reason to start looking for a replacement customer. And never ever rely on just the one customer: your negotiation position is now crap and if anything happens to that one customer, their customers, their market or the relationship then you're done.

If and when you are looking for funding for your healthcare start-up please contact me, I may not be able to invest myself but I do have a whole pile of contacts and some of those are doing regular medical investments.