Vanta - it's a trusted provider with tons of well respected auditors. It's also great to have a public facing security posture, which Vanta hosts for you.
The services mentioned above will help you monitor the technical controls and help with policies to some extent. If you don't have anyone familiar with infosec and SOC, it will be challenging even when you use services like Vanta, Drata, Thoropass, etc.
You will need an independent auditor, which also has a fee. To maintain your SOC2, you will need an annual audit and some admin overhead. For a small startup without too much complexity, $22,000 to $25,000 is common for a monitoring tool + audit. That will be a recurring cost annually + internal overhead + any fractional CISO or consultants you might need if you don't have in house expertise.
But if you have a team who can do the technical work and only need guidance, then you can do a 30 min to an hour per week stand-up with a CISO during implementation and remdiation of discrepancies. then maybe a 1 to 2 hours per month for general issues. Some services often have free consulting as part of their package if you ask them. This will help with the implemantation but if you have lots of things to fix, then it will cost you extra.