How much should I pay an Admin?

Q: What's a good salary to pay a certified Salesforce admin candidate with great high-level intermediate experience in a multitude of industries but no college degree for my start-up company?

Many of the best salesforce admins I know either do not have college degrees, or don’t have degrees in any field related to the job tasks. I would not consider a degree to be indicative of related knowledge. Even those with a computer science degree may not have the necessary Salesforce-related knowledge.
Beyond that consideration, salary is largely determined by your location and market conditions. Given the mission critical nature of Salesforce in many organizations, consider the salary range to be comparable to manager/senior manager level role with specialized skills. If you are part of an organization with a large number of users, multiple salesforce orgs, and/or custom applications, the role could range to director level — especially if they are supervising other employees or contractors, or responsible for budgeting.
The certification is important, and worth paying for, but also ask about their ongoing training and achievements on Trailhead, their goals for additional certifications, participation in any of Salesforce’s ongoing webcasts, attendance in Salesforce events (Dreamforce, TrailheaDX, World Tour) and their involvement in local user group events. This ongoing training and after-hours involvement in user groups should be compensated, if not with hourly wages or comp time, then with an appropriate salary. These investments are important to stay abreast of significant changes and new features in Salesforce, and they provide good value to you as an employer.
Why invest in your employees’ development if they might use that to find a better job? I’m reminded of this classic exchange…
CFO: What if we invest to train our employees and they they leave?
CEO: What if we don’t train them and they stay?
Bottom line, if you hire and support a Salesforce Admin who is well-trained, certified, always learning, and ambitious, that person can significantly create value in your company by increasing the productivity of the operation, introducing industry best practices into your work flow, automating repetitive tasks, improving customer satisfaction with more consistent and speedy responses, provide reports and analytics to inform management decision-making. Expect to value that person appropriately.
One other resource is the Mason Frank salary survey: Salesforce Salary Survey 2019/2020 | Mason Frank.