You need to sell the sizzle not the steak. Nobody needs a website. some business need new business. some need ways for existing customers to more easily schedule appointments, etc...
Also, the more risk you can absorb the better. don't sell websites sell appointments. or take a commission.
To add, look at where you can add business process automation and self service and if or how that could optimise work throughput and reduce overheads. A lot of that has been commodotised in large enterprises but in smaller ones there may be some gains to be had.
Once you get down to one assistant (or a handful), it is not about replacing employees. It is about helping them help customers by reducing paperwork/overheads.
For example: Maybe the vet is 100% booked, but cancellations mean they are idle 10% of the time, or maybe waiting room wait times are above average / bursty due to poor predictions of how long each appointment will take.
Also, the more risk you can absorb the better. don't sell websites sell appointments. or take a commission.