Hi cakeman,
I certainly don't want to disagree with any advice that's been given, because everyone that's responded has a great amount of knowledge and experience with this stuff, so take my recommendations as an "add-on".
I have done the eve mount idea quite a few times.
right now i have a 22 foot fiberglass mast mounted to the eves of my house, and i bought these brackets, and i LOVE them!
https://www.ebay.com/itm/TV-Antenna...743714&hash=item51e5ee9117:g:CV0AAOSw0JpV3z4Z
WAYYYY better than what you'll find in the home improvement stores. thicker metal, more adjustability, and very secure. I highly recommend them.
when erecting a mast that will go all the way to the ground, the amount of "shake" the mast will experience below the guy wires (if used) and even below the brackets, should not be underestimated.
for this reason, i would not recommend using just one of the brackets i linked to at the apex of the eves.
get a couple of 8 or 10 foot 2x4's, and lag bolt them to the eves as far down below the apex as your roof pitch will allow (mine is about 3 feet below the apex).
lag one 2x4 behind the eves securely, then cut the other short enough so it will fit in front of it. (i match the angles so it looks better, and paint them to match the eves).
then screw it to the front of the one you bolted behind the eves. now you have a place to put the lower bracket that will sit flush with the upper one).
if the top of your house sits at 20 feet, and you have a 50 foot mast, then you are going to need two sets of guy wires. one on the top of the mast right at the base of the antenna, and one 10 feet below that.
four guy wires are nice, but really three in a triangle configuration will work just fine.
DO NOT try to get away with just using one set.
the last thing you want is to be worrying about your antenna every time a wind storm comes through town.
I like to use the dacron rope type, as they are easy to work with, and don't radiate like galvanized guy wires can.
they will have a slight initial stretch, but i have found that after a week or so, you can go out and re-tension them, and re-tie the knots and they hold pretty damn well.
3/16" size will work fine and i use these:
https://www.ebay.com/itm/150-1-4-Da...445838?hash=item1e88ff364e:g:MKMAAOxypNtSjVg7
you may need more than that amount.
you'll want to use a "thimble" for whatever size rope you get, like this:
put them in the guy wire collars on the mast, as they will keep the rope from getting cut by the collars over time. you can get them at the home improvement stores.
As for the base of the mast, you need to secure it to the ground in some way.
the depth doesn't matter as far as antenna performance or grounding goes, but you won't want it wandering around.
my suggestion would be to get a 5 gallon plastic bucket, bury it almost all the way in the ground below the mast, and fill it with concrete. then just put the mast down in the concrete when you install the mast.
as for grounding, per NEC code, you HAVE to tie your antenna ground to your main electrical panel ground, so you'll need to pound a ground rod in at the base of the mast, attach it to the mast, and use solid copper wire size #8 or bigger buried a few inches under the soil all the way around the house, and tie it in to the main house ground.
hope this was helpful.
i know it sounds involved, but peace of mind usually is.
LC