What are some of the desired employees benefit that a start-up could provide with large satisfaction impact but little financial cost?

I would look at involving the employees into the company's strategic decisions and find out innovative ways to achieve company goals, thus in the course achieve employee engagement/loyalty. Once you have the financial stability, the company can then focus on providing rewards and benefits to retain the skills/talents.

There are many more but some of them are: benefits for employees are Life Insurance, medical Insurance, retirement plans, disabality insurance, Monthly expenditure vouchers etc.