I was an archaeologist for about 12 years after graduation: of my cohort (about 30 people - 20 years later) afaik, 4 people still work in archaeology, and from those I have dug with (because you need a lot more experience than your degree gives you in order to get paid work in the field) over the years, other than those who were already working with a unit when we met, there are about 5. There are jobs out there, but they are few and far between, and you will need to be able to travel in many cases - also, in addition to considerable field experience, many people also have PG qualifications too: perhaps not from the beginning, but in order to advance, you almost always need to specialise.
My BF was a later entrant to archaeology from another discipline: she started retraining around 26, and is now 50 and working for a unit. She regularly commutes across the North of England, has two specific MAs she paid for for herself, and she earns around £30k.
This isn't to say not to do it - but be aware, it's a lot of hard, physical work, for low pay, if you do actually want a job in archaeology: and if you want to go into academic archaeology, you are going to need to be able to be in the field for weeks on end, which raises issues perhaps over childcare.
Do it because you're interested and passionate (and mature students tend to do very well at their studies, btw) - but not necessarily because you plan on making a career out of it: 4 mature students were in our cohort, but none ever worked in archaeology, which was sad, as it cost one of them his home, his marriage and his family in the end.
It's a great, great life - but it's not for everyone. (Fwiw - I quite because I worked overseas, and had got far enough up the totem pole that I was spending more time on admin and paperwork etc than I was in the field, which wasn't what I wanted. I still miss it - very badly - now: but it was right to quite when I did.)