Hello Richard,
Some very good, practical advice from the others.
I think there are quite a few considerations as well – building space, tools (including machine tools), timescale, budget (?), not to mention distance from sailing water (assuming a working model).
Probably, at the top of my list would be 'inspiration'. This will help carry you through the difficult bits to arrive at a finished model. Have a look at plastic kits (huge variety these days) and Youtube videos. Also, visit the different manufacturers' websites eg Model Shipyard, SLEC etc, and, look at the 'Albums' on this forum to give you an idea of what can be achieved.
Tons of help here once you're a little further down the road…
Dave C