Paid advertising is an amplifier, not a starting pistol. It takes whatever your site, your offer and your follow-up already do and does more of it. Three things need to be true before that is worth paying for, and most companies that report disappointing ad performance were missing at least one.
A page that converts something already
If organic and referral traffic arrive and leave without enquiring, paid traffic will do the same at a higher cost per visitor. Fix the page first, with the traffic you are already getting for free.
The threshold is not a specific rate, it is evidence. You should be able to point at enquiries that came from people who found the page on their own. Until that exists, buying more visitors is buying more evidence of the same problem.
A buyer you can describe to a targeting interface
Ad platforms are targeting tools, and vague targeting is expensive in a way that vague outbound is not: you pay for every impression served to the wrong person. A profile that is still a hypothesis will burn the test budget before it produces a readable result.
This is the argument for running outbound first even when paid is the eventual plan. Outbound tells you which segment replies and which message works, for the price of time rather than media.
A process that can absorb the leads
Leads that are followed up late convert at a fraction of the rate, and paid campaigns deliver unevenly. If nobody owns the inbox on a Friday afternoon, the campaign is manufacturing a cost without a corresponding chance of revenue.
Decide who responds, in what time, and what they say, before anything goes live. This is unglamorous and it is more often the limiting factor than the creative.
What to do instead, meanwhile
Borrow an audience rather than buying one. Partnerships, the events your buyers already attend, and direct outreach to a named list all produce the same thing paid produces, more slowly and with a reusable by-product: a read on which message works.
When you do turn paid on afterwards, you are buying scale for something you already know converts, which is the only circumstance in which it reliably pays.