Start over...that's not a reasonable way to choose a business domain.

It should be other-way around. First decide your niche and then select a domain name based on your niche.

I bought this domain name a long time ago for the hell of it. Have to use it first

So - another $9 investment to acquire a domain name usable for something you might actually want to do will break the bank or spoil your plan to take over the world.

Really? Quit, now!

BTW - the word only relates to the astrological sign, not the disease, but I'm guessing that won't matter, either.

Lol, you can pick that domain but you should write another story that makes more sense to reader, so they can see they benefit from your website.

Actually this is not the ideal way to choose a domain name to start wanting to make money on the net... However, if you are determined to start only with this domain name, then go all out - since you started out because you are born in July, stick to the astro part and not the medical side. In any case unless you are in the medical field, you are not really qualified to talk on an area in medicine.
www.cancerian.com - Everything you wanted to know about Cancerians.
Do your research - there is enough material on astrology and the sun signs for you to make a lot of sections on your site - About Cancerians, Cancerian as a father, mother, partner, Cancerian kids, Cancerians get along best with with other sun sign, which signs are not best fits for Cancerians, What does the 69 mean for cancer, Why is it called cancer, What is the emoji for a cancer, Which sign is most compatible with Cancer, What is a cancer's soul mate - and 100s of other stuff...you can also be an affiliate for some cancerian paraphenelia like t-shirts, bracelets & other jewellry etc.
start with all this and see if it makes you happy and also whether it make you money - once you have a lot of content and some traffic, you can also monetise it with adsense

Thankyou. You've given me lots to think about

That's fantastic.

Just search for any related affiliate offer that you can promote and then write articles or blog posts around the subject.

I think the first step would be looking at what you want to do, then deciding on the domain.

If you do go the horoscope route - will it only be geared towards people that are in the cancer category?