If you set it up from scratch, you should continue to work P/T or F/T for someone else since your new office will not have enough patients to fill your appt book 5 days/wk at the beginning.
When my sister set up her office, she told the landlord that the 2000 sf space was too big and she only needed 1200 sf. The landlord agreed to put in a partition to shrink the space to 1200 sf (at no charge) and this helped save my sister a lot in construction cost. It was plumbed for 4 operatories but she only bought 2 chairs. She later added 2 more chairs because I came to do in-house ortho at her office. At the beginning when it was slow, she only worked 3 days/wk (Saturdays and Sundays) at her own office and she worked 4 days/wk at the corp office. In addition to the $100k loan for office contruction, the bank also gave her $40k working capital but she didn’t use it because of the positive cash flow from her corp job. Instead, she used this $40k amount (+ $60k of her and her husband’s own saving) to invest in a commercial building with our uncle, a family MD doctor, who became very rich from estate investments. She had earned about $1k/month in rent from this commercial building. This commercial was later sold for 4x the original purchased price.
I set up my office 3 years after my sister set up hers. I hired the same contractor who built her office. Like my sister, I also kept my F/T associate job at the corp when I started mine. It was much easier for me than for my sister because my ortho associate job paid me a lot more and my wife is also a specialist. My sister and her husband don’t make as much as us but they are currently ahead of us financially. That’s because they continued to live like students right after graduation (ie living with our parents for 3 years), they didn’t drive fancy cars, and they started investing very early. When I started investing (in 2008), my sister already had 2 rental properties.
As Tanman pointed out earlier, you should start cheap….only buy things that you need. You can always upgrade to more fancy equipment later. A new office doesn’t have to cost $3-400k to set up.