the answer is "it depends!"
worst case scenario (not really), you are older (past 40), with a family (wife and kids), and a full time job. this means you probably could spend 3 days a week, two hours a day, for training at the dojo. that sort of training schedule would be the bare minimum to slowly increase in skills for one art. also, at higher age range, your body isn't conditioned to take the kind of falls for judo (ukemi in judo is mostly breakfalls with the other bugger land on you on the way down), i.e. your recover time is much longer than when you are young. so if you are younger and has lots of time and energy on your hand, then i'd say go for it. if not, then "it depends!"
majority folks came to my dojo have no previous martial art training. not a problem so far. depend on the teacher's background, he/she can bring skills from other arts into aikido training regiment. so it depends.
personally, i would rather pickup karate or kungfu or wingchun or some striking art first. many folks in judo and aikido are lousy at punching and kicking. if you notice that in aikido, you spent half of your time attacking, and if your attacks suck, so are your aikido techniques.
so true ".... many folks in judo and aikido are lousy
at punching and kicking...."
I would guess that not many aikido yudansha can NOT stop the bare knuckle punches from a kyokushin/enshin yudansha.
...and a solid, penetrating, punch to the face can take down an assault, real fast.
I have many years of karate and am still honing my punch (and kick), at home garage gym and when I drop-in at my old karate dojo (which is infrequently, since I'm focused on aikido).