Wait To do it big or start it small now?
Small
Small startups have small risk factors and small return. If you are an expert in the field of business you enter, you know what will be the risks and benefits.
A new business always faces some running problems, that is quite natural. It can be solved in less effort and time because it is a small business, the problems are also small.
The same in returns, what you get a return in your business also small, when comparing to the expense to run the business, the returns might be less than the need. So there it can be called a Loss. Up to increase the return you have to bear it.
Keep some reserved fund to keep going until you get your flow.
You can clearly plot the and monitor all the works and process of the business when you start it small. You can make corrections, easily understand the pros and cons.
You can build your network, management, and processes to exact results and statistics. You are in control of your business. Then you can expand step by step on the foundation you laid. Expansion can be quick and big because you are just adding more things to the well-plotted, well-executed system.
Big
Big will give all big. Risk and return. Starting a big run is always a great risk. How expert and experienced you are, you have to face some problems in the business. If it is a big step, things coming on the way will be big.
A bigger startup needs more manpower, more money, and more monitoring. Making changes and rebuilding structure in a running big business is not an easy task. If you stop for a few days for your modification or corrections the loss will be very big and following on will be very hard unlike the small.
If successfully done the return also big and there is no need to look back. But the risks are also heavy. So, avoid the big step.
My opinion
Start with small, build it well and monitor it, if you feel the business is in your control then expand it. That will lead to success.