Welcome to the Ranch, Jane!
I don't have a CS degree and I was a database application developer for 20 years, so it's certainly possible, although age will be a factor in finding regular employment: you are older than the typical junior DB developer (and IT is plagued with ageism) but of course you also have a lot of very marketable skills and experience. If you were looking for full-time employment, I might suggest you consider working your way into IT via business analysis, because your background would seem to be very relevant here and (in my experience) public sector IT projects are often knee-deep in business analysts, architects and a whole raft of other expensive consultants, so there ought to be opportunities in the DC area. The big consultancies tend to get a lot of this work, so you'd probably need to start with them if you wanted to go down this route.
As you're looking at clients with smaller-scale projects, you'll need to think about what kind of work they are likely to have, what tools they are likely to be using (or would be good for them to use), and how you can acquire the relevant skills/experience. If you're looking at schools and non-profits etc, you might want to focus on free open source software (FOSS) e.g. MySQL or PostgreSQL database,
Java or Python programming language, but be prepared to deploy your application on Windows or Linux. Here in the UK, for example, there is a lot of pressure from central government on public sector organisations to use FOSS for future projects.
Your current project is Microsoft-based, so you already have some experience with MS tools. MS Access/VB is fine (although perhaps out-dated) for a small stand-alone project running on a PC in an office. But as a would-be database developer, you will need to go beyond MS Access and start exploring more flexible tools and technologies that are used by a wider range of organisations. If you think your target market will be exclusively Microsoft-based, then you could opt to scale up into more modern MS tools e.g. SQL Server and C# on .NET, as these are still very flexible and should feel familiar, while Access and VB are something of a dead-end.
However, there are a lot of options now for hosting applications remotely e.g. on "cloud" services like Amazon AWS or Heroku, or as web applications on a conventional internet hosting service, and these are typically based on FOSS tools such as the "LAMP stack" (Linux, Apache webserver, MySQL, PHP/Python). So it would be good to keep your options - and those of your clients - open by not tying yourself exclusively to a restricted proprietary platform.
I would suggest that when you complete your current MS project, you build on that experience by re-implementing your current project using FOSS tools. It doesn't need to be perfect or have all the bells and whistles of a commercial solution, but try to implement it as a full-stack web application that demonstrates each function you think it might need e.g. some browser-based user interface screens, some CRUD functionality, a simple reporting or CSV data export option, and a login mechanism. If it works out, then you might put this on Github (or even run it as a live demo on an internet hosting service) to show-case your skills. If not, you will still have learned a lot of useful stuff. It's important to bear in mind that a database application developer needs to know about more than just databases, especially if you are going to be working largely alone on small-scale projects without lots of other developers to help you.
In terms of technology, my background is Oracle RDBMS, but I now work with open source Big Data tools, so my experience is not necessarily relevant to your target market, but I can suggest some things to look at:
I would suggest you look at learning a modern programming language e.g. Python, which is open source, easy to learn, object-oriented and widely used, as well as being eminently suitable to the kind of small-scale projects you are looking at. It's also replacing VB as a scripting language in many third-party tools. This thread includes links to useful material for learning Python. If in doubt, start with Head First Python as it's a lot of fun and covers a lot of topics at an introductory level.You'll need to pick a FOSS database platform, and many people use MySQL although I prefer PostgreSQL, but either of these would be a good option. They are both well documented and mature, so it should be easy enough to get help if (when!) you get stuck. I would also recommend you learn a suitable web application framework e.g. Django is a good choice for Python, as this will save you (and your clients) a lot of pain by handling a lot of the complexity of a typical database-backed web application, and you will be able to make progress a lot faster than by trying to do all this stuff yourself.Most web app frameworks use some kind of templating mechanism for the browser UI, but you may want to pick up some basic web development skills to customise your application's user interface i.e. a bit of HTML, CSS and possibly JavaScript. You might want to ask around locally to see if there are any amateur web developers who might want to collaborate on this stuff, as it might save you a lot of effort if you're not a UI designer by nature and it would also be a good opportunity to network with people you could work with later on.
I know this sounds daunting, but you don't need to master this stuff all at once, just use your demo project as a scaffolding for you to build up your skills as you go along.
In terms of your database skills, it sounds like you are already learning, but you might find some of the stuff
I posted about databases 2 years ago is still relevant. Take time to learn SQL properly - not just SELECT/INSERT/UPDATE but also the more complicated stuff like aggregation functions etc. Learn about indexing and key management i.e. which columns should you index, when should you not use an index, and so on.
I would also recommend you pick up a book about relational databases and data modelling e.g. an introductory college textbook, or try the
free online course on databases from Stanford. I've worked with a lot of CS graduates, but I've never met one who learned anything much about databases in college, which tended to have fairly disastrous consequences when they insisted on implementing database applications without adult supervision. So by learning a bit about how databases work, you can put yourself ahead of most CS grads in terms of database skills.
Finally, you might want to start looking out for trends in the industry that might be relevant for your career plans. For example, Big Data and data science are growth areas, where a mix of coding, database skills, numeracy and business knowledge can be very marketable, and you might decide you want to move into that area at some point. NoSQL databases have become popular alternatives for some applications e.g. MongoDB is quite widely used (one of my colleagues has used it for a web app for a local charity) and you can learn about it via their regular
free online courses.
OK, enough rambling from me. I hope some of this is useful, and best of luck with your plans!
