Buy once, cry once. Yes and no. Great if you can afford what you want now. But if you need something now and don't have the money...
Currently using:
FOH:
2 JBL eon 15's (the generation before the latest). $700 on CL with rolling gator bags, cables and stands.
Small places, vocal, keys, guitar in PA. Larger places we add a Mackie 15 powered sub and run everything in the PA. Even bigger or outside we add a second mackie. The subs belong to the church (who says religion has no benefits?

).
Monitors: 2 db powered 12's and 2 15's. Belong to one of the singers.
Mixer: Just got a Mackie dl1608, haven't used it yet.
It's a very flexible system. Sometimes we just use the db's for smaller, quieter things.
My PA journey: Bought 2 Peavey 12 monitors for my first band that already had a PA. They fried them the first practice. Replaced with 2 Peavey 15 wedges.
Got Peavey 6 channel mono powered mixer to use with monitors as mains. Didn't realize at the time I needed a separate amp for monitors. I still use this head in my basement.
Church owned Mackie 808m with Community 15 mains and my peavey monitors. More than adequate for a 5 person cover band in a 50-150 room. Add powered subs as needed. The mackie will run at 2ohms so you can chain 4 monitors.
Yamaha 6 channel powered mixer with club 15 mains. CL $550 with stands and cables. Wish it had 8 channels. Good sound. Heavy tops. 4ohm minimum so only 2 monitors.
Church owned mackie 16 channel mixer, 2 qsc amps, off brand 15 mains. Good. Heavy. Needs external effects, compression, reverb, etc...
Mackie 12 channel->yamaha 16 channel->Mackie 1604vlz->Mackie dl1608
Need more inputs causing each upgrade. Got the yamaha on CL for $115 with case. Sold for $250. Didn't cry either time. When we went to the used 1604 I didn't realize it didn't even have a main graphic EQ or effects. So we ended up with a heavy road case and outboard stuff. The new 1608 is 8lbs and has everything we need built in.
TLDR version: Powered mixer will get do fine for vocal PA. Add a sub if you want kick. Good deals on the used market, especially if you don't mind heavy. Look hard at features before you buy. Most separate mixers don't give you graphic EQ on the monitors where, IMO, you need it most for feedback control. Powered mixers do. If you have to add outboard EQ, comp, xover... your good deal may become a PITA.
If you've got a lot a cash get nice stuff now.
If I lived in CA I would probably have tried Carvin. The PM stuff is light and cheap. But I don't want to deal with shipping if it breaks.