My big plot used to look like a marshy lake every winter so I when I took it on I decided to go for raised beds. After 3 years of working it, I learned the reasons for flooding was:
1) my ex-neighbour had dug a channel off his plot to drain into mine
2) it was at the bottom of a hill so will always have a higher water table
3) the council tractor had compressed and compacted the heavy clay soil (and subsoil) after an annual trim so water was never able to drain away.
At first I used the plot just for summer crops but after digging and creating the beds, it is now a very productive plot throughout the year. The channels were filled in and boundary footpaths resurrected so that stopped the drainage. Even digging through the compacted soil was enough to reduce the flooding problems, but being at the bottom of the hill actually has its advantages - I don't need to water the plot in a dry spring or hot summer half as often as those at the top of the hill
The raised beds are made from wood collected from skips - several short lengths of floor or roofing joists or old skirting boards etc - so doesn't look neat & tidy but it does the job of raising the soil enough to allow gravity to drain off excess water and hasn't cost me a penny. And don't forget you could use things like old tyres or old bathtubs if you can get hold of them. No top soil for me but anything compostable & manure, and the occasional bags of sharp sand if I want better drainage eg herbs. I won't deny it has taken a lot of effort but well worth it.
So to answer your question pvc - if you are prepared to do the work and keep at it, go for the plot. As for expense, that is entirely up to you. The other reason I might suggest why it might be a good idea is that it is unlikely the plot has been cultivated much if others have avoided it so the number of pests and diseases are more likely to be much less than that of an established plot & will work in your favour