I don’t have a heavy beard. I usually shave every other day. I haven’t shaved for a week now and it’s at that “you look like a homeless bum” stage. (maybe I should at least shave my neck, huh?)
So, how long can I expect to look scruffy untill somebody says “Hey, nice beard”?
Shave your neck. A clean neckline shows that the hair is due to style, not slovenliness. But to some, you will always look scruffy. Your Mom, for example.
Everybody’s facial hair growth rate is different. Mine grows in a a snail’s pace, but at least hardly anything grows on my neck.
Unless you’re Raffi, keep no hair on your neck.
If your “beard” grows like mine - forever. 
I’ve gone a month without shaving before, and I never got past the homeless bum stage of scruffiness. It was long scruff, but it was far too thin to be legitimately called a beard and/or mustache.
It looked like crap, and no amount of trimming or grooming was going to fix the problems it had. The only solution was to shave it off and keep it that way.
I’ve got sparse facial hair - especially on the cheeks - and I know that I could never grow a beard there that didn’t imply late-stage mange.
I can grow a van Dyck, but there are complications - my facial hair is roan (about half the hairs are brown, half are blonde, and they’re interspersed so there aren’t particular dark and light patches) so that if you’re not looking at it in the right light you only see some of the growth. Insult adding to injury, everything below the jawline is black and very visible.
On experience, it takes three weeks to look more than unshaven and about four weeks before it looks as though it’s not just the stylings of a crazy person.
Mom’s dead. But I’ll take your advice and shave the neck.
I disagree. Well, not about your mum 
Let it grow to a decent length so you can decide what to cut off. Cutting early has a fairly high chance of cutting off the wrong stuff/too much and it will look shitty.
For what it’s worth, beards.org agrees with me.
ETA: beards.org says 4 weeks.
Oddly enough, my facial hair used to be like this until about a year ago, after which point it turned uniformly dark. I had light blond hair until I was about 5 years old, then it gradually started turning darker until it’s now very dark. (It still has very bright blond highlights though, when it’s under the right kind of light, as is extremely noticeable in the small picture in my user profile.) Since my normal hair took a while to get darker, I guess my facial hair was the same way. Maybe as you get older the lighter spots in your beard will disappear?
My scalp hair’s always been dark brown. I’m assuming that as I get older, I’ll probably trade the blonde for grey and I won’t really notice - especially as I shave my scalp.
Like the OP my beard is light too, I can get away with shaving every other day. But the downside is when I’ve tried to grow a beard, it never fills in well. Now that I’m 45, most of it has turned white so it looks even worse.
As another poster said, sometimes beards just don’t look good. It’s kind of an individual thing.
When you have a beard, you still have to shave (your neck) and groom it, otherwise it looks bad
I should add that my recent embeardedness was due to four weeks off work, at which point I shaved it off.
Out of interest, does anyone with tightly-curled facial hair know when it stops itching like a nest of ants is eating your face? It seems that it takes longer than 4 1/2 weeks.
Agreed. Shave the neck.
After another week, it should look like a beard is on its way even though it isn’t quite there yet.
Has it started itching yet? Its been eight years since I last shaved my beard, but I do remember that itch.
Mine took about three or four weeks to be presentable. Yes, shave the neck; go to a barber if you must. I’ve had a beard for just over two years now, after going my entire life without one (if you don’t count my misbegotten attempt at one in college). By necessity, it’s a goatee - the hair just doesn’t grow in between my chin and my ears. Having a beard certainly makes for a faster start in the morning, since you don’t have to spend nearly as much time on shaving. My wife likes it, too.
Before (I’m the tallest guy, third from the left): http://www.acslaw.org/files/images/IMG_0115_edited-1.jpg
And after (I’m the guy in front with the blue tie): http://www.acslaw.org/files/NE%20Ohio%20New%20Committee.jpg
IMHO, beard is better. YMMV.
There’s so much individual variation with this. My first bf in college tried to grow a beard, and it just kept looking sparse, even after a few months. Mine can start looking good in about 3 weeks. My partner, who is Persian, already has 5-o’clock shadow right after he shaves, and there’s noticeable growth in just a few hours. He could probably grow a full beard in days.
I agree. It’s amazing how a beard intensifies the eyes.
All right, then, I’ll keep it! 
I’ve had a beard forever – well, ever since I was 17 years old, and grew a beard to celebrate the end of high school. Back then, beards were unusual enough that I got my photograph in one of the Sunday newspapers in Sydney. But I grow a lot of hair on my chin, and my main problem has always been trimming it so that it looks reasonably tidy.
Alternatively, keep the neck and shave everything else.
The neckbeard.
Two things. Keep your hands off it! The temptation will drive you nuts, but itching is worse. Rub olive oil into it a couple times a day until it gets long enough to stop trying to hurt you.
For some men, it will be an endurance contest between the man’s patience and the period of time when the beard looks awful and feels strange. If he can outlast that, then he can properly decide whether the beard is worth keeping. I knew one chap who grew a King Tut beard out to 6 inches before deciding to shave it off. It was starting to look kinda cool, too.