I’m just a hobbyist here giving advice.
The hard work here isn’t laying a component on a board and routing some traces. It’s designing the schematic for the circuit, looking for flaws in the schematic design, working out a board shape that will hold the parts and meet your physical constraints, selecting appropriate design rules for the application domain (which, given that you are talking about a relay, includes being specific about voltage and current capacity, and current capacity depends on physical constraints for dissipating heat), choosing components that meet your needs (including connectors that will be safe given your constraints), laying out the board, checking the design for defects including thinking through potential failure cases, etc. You bring up a relay, so you are probably doing this in order to switch a high-voltage and/or high-current circuit, possibly switching AC.
As a hobbyist, I’m inconsistent in knowing what could go wrong — there’s a reason for engineering certifications here! I know some of the things that can go wrong here, but I’m not trained in all the things that are reasonably likely to go wrong. I can imagine some things? What happens if your relay welds closed and doesn’t turn off? Does it create an unsafe condition? Have you properly separated low-voltage and high-voltage sides of your circuit board? If you are switching AC and decide to replace a physical relay with a solid-state relay (SSR), do you know that its common failure mode is to fail on? I’m not giving legal advice of any sort here, but if I personally were selling electrical devices I would be getting advice on liability…
Reality-check, since you say you are in it for the money: The high-value things you can do in the market with an embedded network-connected computer and a relay are vanishingly small. Make sure you are aware of what people are doing with sonoff switches, which are based on the 16-bit ESP8266 predecessor to the ESP32, before you invest.