Guineas are lovely creatures - very chatty, all different piganalities and quite vunerable so you yearn to cosset them 
They need protected from ;Heat (I find it trickier to protect them in Summer), damp (they are prone to respiratory issues) draughts, extreme cold (Yes, I know wild cavies live in Peru where it's cold but mine have never been further than Kent )
Boars or sows depends on your preferance. Boars are very cuddly love sponges but you need to give them LOADS of space. And they have a boary aroma which is not at all unpleasant , some of ours have been Boarier than others.
Mine are all Rescued as adults apart from GP3 who was 6 weeks.
Amazon are good for things like cages/runs (Bunny Business are good. We don't look at Guinea things, we go Rabbit
Provided there's no mesh base, and the gaps in the bars are small enough, bunny cages are bigger, higher, sturdier)
Be aware of allergies to fur and hay.
Read up on common piggie illnesses and what foods they should have and mustn't have.
They are messy ( soooo messy) . We put ours out this morning ( my trio have a 4x4 run attatched to a 4x2 rabbit hutch) my 2 sows have an 84" x 48" rabbit run with boxes and tunnels.
Fresh newspaper in the hutches and they were able to choose if they wanted shade with a nice breeze or grazing.
The inside of the hutch looked like it hadn't been cleaned for a week, these animals pee/pooh for Britain 
We clean their bedding daily , its the only way we can keep them comfortable.
They can get problems with their feet and their very low slung bellies on dirty bedding (I have no idea who owns these piggies that only need cleaned weekly. Mine are never that tidy)
We have a wooden playhouse (used to belong to the DC) that DH has customised for the pigs.
They have indoor C&C type caging (very useful and adaptable , folds away flat) and a 4'x2' plastic/bars cage.
And their runs/hutch/box
This year I have to organise indoor accomodation for 5 .
GP4/GP5/GP6 slept in the 4x2 last winter (only at night ,we gave them fleece , a rubber trug house and hay cookies with a blanket over the cage) in the small bedroom.
This year I also have GP7/GP8 so I'll make a night cage for them with the C&C..
DH dreads when I say "Oh, I've just thought of something for the guineas..." because he has to make it.
I do ideas, he builds it 