My first question would be, have all your users paid the $70 upfront, or is there a chance that some of them might cancel and get refunds? In order to make sure your economics make sense, you need to take churn into account and it's not 100% clear to me whether this is the case.

Assuming that you do have churn under control (and therefore that your product does have a clear benefit that a fraction of your users are willing to pay for on a repeatable basis), my next step would be to assess market size. The spectrum ranges from 19 people (your current users) to 1b+. What you could do would be to try and run a slightly larger campaign and see if the numbers still add up, ideally spending no more than the proceeds of your previous campaign.

If things work out well, you might even make this a self-funded business, in which case you wouldn't even need to search for an investor ;-)