It all depends on what contribution you want from the barrel.
A barrel that has been used for spirits, you will get the influence of whatever spirit was in the barrel last.
Ditto with a wine/port/sherry barrel, although the bugs from sherry will start doing their thing on the mead.
The freshness of the barrel counts as well.
A french white oak barrel, uncharred, will be different than a Sinatra cut high char.
Ideally the barrel needs to be full. Will you be able to fill it all the way up>
A ten gallon barrel can typically hold~11.5 gallons, and depending on how long it ages, it will need to be topped off due to absorption of the wood and the thieving angel.
How long do you plan on aging and will you be able to replace it quickly upon emptying the barrel?
I have three 10 gallon barrels.
Two can from Sons of Liberty Distillery and one from Black Patch Distilling. The first two had whiskey and are now sour solaras, the third had rye whiskey and has had a RIS, Olde ale, A Belgian Quad, and now a belgian Golden Strong.
Due to my new position, I'm not home very much and work ~5000 miles from home. The quad spent too much time in there and is too oaky, and will need another beer brewed to blend with it to "tone it down".
So as you see, one can become a "slave to the barrel" and you need to like barrel aged drinks. It's been in there and needs to be replaced, it will seem that you are always having to brew for the barrel, I realize mead is different and takes less effort, but there can be a greater expenditure. And if it goes sour, are you willing to accept the fact that it is what it is and the barrel will have to be retired or alway make sour products?
Just a few thing to think about.