There are three things a startup has to have as core skills.
One is technology.
Every business is now a technology business - it is through technology that services are delivered, promises kept and relationships managed. The technology delivered customer experience is often a potential buyer's only point of reference in making a buying decision.
The second is Marketing
Marketing is no longer sending a few emails or putting up some ads. It is a science, creating an image and proposition people relate to and are attracted to, a buzz which spreads the idea to engage media, influencers and connectors, and a frictionless and motivating path to purchase or partnership.
The third - and note it only comes third - is what you offer. Product or service, delivering it with empathy, engagement and enthusiasm all with an underlying competence is vital to create confidence and reduce the value of alternatives.
Sales, by the way, come as a result of all three of these - they are not a discipline in their own right. Having a salesperson push product on people one-to-one is waaay to expensive to scale and businesses who use this method are finding margins plummet and resistance to the interruption almost 100%.
It is also fixed in the idea that you don't have an ongoing relationship with a customer, but merely take their money once and walk away to spend all that time and effort all over again on finding another new prospect. In a connected world this is lunacy, yet it is encouraged by most sales commission models.
Having a 20 hour a week ex-salesperson as a key player in your startup is a guaranteed route to failure. It will send your company the wrong way on customer experience, on retention and on user growth.
What is more worrying is the fact you are even considering it. This shows you don't have a structured marketing plan, linked into to your core technologies to give you metrics on user growth, churn, spread of influence etc. It shows you are still trying to work a "fixed product, sold once" strategy.
A root and branch review of what you're doing and your plan to do it is required.