> My thinking around that is it's pretty much the same effort to build something small or something big
Your thinking have huge mistake, because you thinking about money, without considering market.
What I mean, market is not a single flat place where all 6 Billions walking and you will look at them from crystal tower.
But real market space is multi-dimensional, for simplicity I will tell analogy.
Imagine, Newton method of finding roots of equations. For simple case it could been considered rough 2D surface, like Moon surface projection, with indefinite number of holes, and some holes are huge, and others are tiny.
And height of edges of hole, which you research are important, because they are practically proportional to energy need to overcome edge of your hole, so it defines some tension, or budget to come to other hole, or it named enter barrier.
And hole width define, how many money could be here.
What important for business, as I said before, you are not only person on Earth, there are at least hundreds millions smart people (about 10%), who also want to make some money and making research of their environment, so your concurrents are aware about surface line of market, and where it have holes.
And typical human avoid small holes, prefer to enter large holes or even huge holes.
So, when you enter tiny hole, huge probability, you will not see any market concurrence there.
What also important, start small doesn't mean, you will not become big any time, as you could make some fat in small niche, and than you could make try to enter bigger niche, or few neighbor small niches, etc.
In reality, McDonalds and Walmart began in regional small niches, and enter mega-cities after make fat in niches (for mcdo way you could watch "the founder" cinema, for Walmart, read "made in America").
Sure, if you have few spare Billions, you could start already big, but I bet, you would not ask this question having Billions.
PS any way, you are not alone, ask if you consider cooperation.