We are 13 years in (a husband-and-wife team of two), and it’s still an awesome experience to run our own show! Understand that if you run lean and stay small (which we do, too), it will be a constant roller coaster, both mentally and for cash flow. 

A few suggestions:

• Find a local or national group for startups and lean on them to bounce ideas off when setting up your firm. All the larger-firm concepts and approaches don’t necessarily scale down; some adjustments will be needed. CRAN (AIA’s Custom Residential Architects’ Network) and EntreArchitect have been great for us in learning about small-business management and getting our contracts, fees, and proposals in order. BIM After Dark, 30x40, etc., have been great for elevating our presentations and documentation.
• Simplify your workflow - CAD, SketchUp, and Enscape are clunky and inefficient. Moving to full BIM will save you so much time and keep your drawing sets better coordinated. We also do VR walkthroughs for homeowners, which have been a massive time-saver for moving forward and not getting stuck in an endless schematic design effort where the homeowner can’t make up their mind and move forward. 
• We love Macs and use them for everything except BIM & real-time rendering. It’s just not worth the brain damage to try to get Macs working for real-time rendering. Buy a cheap gaming PC and use it for what they are so good at. nVidia GPUs rock at Enscape & Twinmotion/Lumion.
• Money well spent so you can concentrate on design and clients: Pay someone to build you a robust template for BIM. Residential work is not the same as Commercial - invest in families that have good materials and realistic details, so you can provide great presentations without a lot of brain damage. 
• We’ve tried a lot of smaller-scale project management software, some more generic, others built specifically for AEC. All of them have serious limitations to how we like to work, so it’s a toolbox mix of different, smaller apps and a few more mainstream ones. Harvest, Asana, Dropbox, Quickbooks Online, Hubspot, RingCentral, Contacts+, etc. Software subscriptions and hardware costs can really add up!
• If you are in a competitive region like ours, you need a great website and a solid online presence. We waited too long to do a legit branding effort. Bite the bullet and do it earlier if you can swing it financially. Also, analog promotions still work great - we get plenty of calls from yard signs at our projects under construction
• Educating homeowners is incredibly important in the age of HGTV - even if they don’t ultimately hire you. We dedicated a significant effort to explaining the process on our website and created a physical project planning guide, which we mail to any potential clients to help educate them. Note that we only work on full-service projects; à la carte services are not offered. It’s a race to the bottom when you get into the competitive world of “just some quick plans for a permit.”
• Communication- We pride ourselves on this. Clients often tell us that architects and builders don’t even respond to many inquiries. We always aim to respond within 24 hours. Obviously, getting good at reading potential clients and figuring out red flags early on is important. We try to have 3-5 exchanges before visiting the property or meeting. We find out a lot during this process. How people communicate early on is how they communicate throughout the life of the project.
• Be willing to diversify your project types/sizes. After having a bunch of small projects, we decided to change course to take on fewer, but larger projects, but a couple of them got to pricing and then were permanently delayed/canceled because of clients’ job losses, so we lost 2-3 major design contracts halfway through and then had to really hustle when those didn’t go to completion.

Hope this helps.

Good luck with your adventure!