The age old 'when to spay' debate

Alright folks, I know this topic has been posted a million times and I'm trying not to beat a dead horse. Buuuuut, I've been doing a lot of reading on the topic and I hear all kinds of opinions on both sides of the topic. I wanted to try to get some opinions from other Beagle owners. First of all, I know all breeds and even dogs within a breed can develop and mature at different rates. I've always owned male dogs up til now so I have never dealt with this aspect of dog ownership, and with this, I am trying to learn as I go. When do Beagles "typically" go into heat, and what is "typically" the best time to spay them? Coming from male dogs, and normally larger breeds at that, I've gotten used to the 'let them mature and grow, then alter' mentality. With that being said, the idea of altering a pup so young scares me a little. Okay, I lied, a lot. From reading it seems most places tend to agree that anything before 6 months is too young and even can pose problems. I read some 'never too early', some '6 months', some 'before her first heat', some 'after her first heat', some 'not before 12 months', and a few 'let them fully mature' and everything in between. With all that's out there it leaves me wondering when is the best. Of course, like mentioned, I've kept many larger breed males and normally I would wait til they were fully mature that way there weren't any problems with growth/maturing. My new(er) Beagle stays indoors in a kennel while I'm at work with no other dogs around. She goes outside in a fenced back yard at night, while I'm out there, to play. We often times go to parks (not dog parks, just parks with nature trails and similar, to do some walking), on walks through the neighborhood, and the lake (when it's warmer out so she can play in the water) - all of which are on leashes and supervised. I know unwanted pregnancies are one of the major concerns for spaying sooner than later. In this matter, I don't have much concern as she is always close by and supervised or by herself. I keep thinking about taking her in to get her spayed but then I just think about how young she is and how much it scares me to have something like this done at such a young age. Anyways, thanks for reading at length, and I look forward to hearing from some actual Beagle owners.