Nursery ? I once had aspirations in this direction. Best thing I ever did was to buy 200 container plants without planning anything ... I then spent every day watering the bl##dy things with a hosepipe. No sooner had I reached the last of them, then it was time to start again with the first. Talk about 'fire-fighting' ...
That was a valuable lesson which taught me the hard way to get everything ready (especially drip irrigation) before stocking-up with plants - otherwise you don't run a business, it runs you ! I mean - would you put sheep or cattle on a field - and only then think about erecting fences ?
A really good tip I got from a business advisor was 'to know your market'. Growing the plants themselves is what I (and every other bloke, apparently) tended to focus on - but the really important bit with any business is sales - i.e. how best to go about relieving people of their money. So - if your market is small, or (say) rural - then you might want to think about selling plants by post, and how best to go about doing that.
If you're wholesale - which retail outlets exactly are going to buy from you, and can you always meet their requirements/demands ? That needs research.
If you're retail yourself (which is a better option for a small start-up) - then you might find yourself hanging around all day on the off-chance that the odd customer might turn up. There'll always be a need to have at least one person on a retail site during opening hours, which can be expensive and/or demanding of your own time.
There's also the issue of 'time-windows'. Flowering plants in particular sell best when they're flowering - because they're attractive at that time. Evergreens, especially conifers, will sell at any time of the year providing they're containerised. Ornamentals sell in one's and two's - hedging varieties sell in the dozens or hundreds - but - with a much lower individual price tag.
But if you really are short on time, then livestock appropriate to your size of land might be a better option ?
LJ