How do we value our startup company when we want an investor to invest?
You can value it how you want, however an investor has to agree with your valuation. If you have ever watched the tv show Shark Tank - a very high valuation is a quick way to END the investor conversation.
The revenue / EBITDA multiplier is typically based on your "revenue growth". Startups growing revenue 2-5x a year have a higher multiple than a startup growing revenues 40% a year. There a lot of factors that go into the calculation and each investor will have a slightly different formula they use.
If you have only been around 2 months or have little to no revenue, revenue multiples don't work. I would start with a conversation with the closest business accelerator or business professors in your local area.
Tech startups typically have higher multiples as well.