One thing that is really important to remember is that you must get enough sleep for your body to recover and "recharge".
You can't automatically just add your biking to an already jammed full daily calendar of things to get done. Your stress level will be off the charts. You need to be able to manage the stress of running your business, yet allow enough time to both relax and allow for at least 15 min to 20 min of riding per day.

You cannot simply pile more on to your plate. Well, you might, until you overdo it and reach a "breaking point".
Riding 50miles in one stretch is not hugely important!
Hopefully, just getting some riding in on the bike makes you feel good (relaxed and de-stressed).

Obviously, it is somewhat of a weather permitting factor, that will determine when and how little that you may be able to ride during late DEC, JAN, FEB, & early MARCH. If you are fortunate to have superb employees who possibly can keep things going well enough as you perhaps delegate more tasks to, that would allow you to "break-away" from the office to enjoy those sunny afternoons when the weather is suitable to "therapy on the bicycle".

It would be great if you can find a park closeby that is large enough to allow you to ride 3 mile stretches without any traffic worries. You then simply repeat the approx 3 mile loop as if it was a NASCAR oval track. Don't worry about speed!! Just ride for the fun of it, and try to relax and enjoy the scenery! ALWAYS DRESS IN LAYERS, WARMER THAN YOU MIGHT NEED TO, AS YOU CAN REMOVE WHAT YOU DON'T NEED AND BUNCH IT UP IN YOUR SEAT BAG.
Others might disagree but I believe that a large park with roadways within the park and/or Park-greeneway paved patths is the best way to simply and safely get back into the swing of riding bicycles. Why? There are No or Few Automobiles and those automobiles on park roads will be travelling less than 20 mph. The roads within the park will be streetsweeper clean every day, so you have no worries about broken glass, jagged metal, and other road debris. Parks sometimes have their own hazards such as wildlife and at times criminal vagrants-perverts that are much more of a hazard than any wildlife species. If the park has rangers or/and security, it might lessen the risk from "humans" so that risk is extremely low. There is never a NO RISK situation but you MUST weigh your RISK every-time you do decide to ride your bicycle on open public roads & streets. Time of day and natural car/SUV/truck traffic can make one heck of a difference, as can prevailing weather conditions (bright sun, clouds-fog, rain, mud or snow, slush, sleet, ice, and/or high winds. A great majority of SUV/automobile/Pickup Truck/JEEP drivers simply do not respect bicycle riders on the streets/roadways. Exactly what is meant by this statement is that these DRIVERS are so obsessed with getting to where they are going on Time, and most are already on the verge of probably being late that they simply DO NOT enjoy seeing a CYCLIST that they view as slowing down traffic. These "Bad-Attitude" drivers are everywhere and then you'll see the One Arm Phone Holding-BAD ATTITUDE drivers who are distracted while driving. Remember High School Physics Class, well consider what happens when a 3800 pound automobile just lightly taps a 20 pound bicycle with an 180 pound rider aboard.........it ain't ever good for the cyclist.................no accident lawyer can get enough for the cyclist client to make that cyclist whole again. Sometimes like the old "Gambler" song goes, you gotta know when to hold em, know when to fold em.............................CYCLISTS must realize that sometimes you got to know what roads you can ride and know where you can never ride, as there is too great a risk that you'll get hit and become a statistic. RIDE SMART! Maximize your visibility by wearing highly visible attire and lighting for low-light situations. On a bicycle, the shortest route is not necessarilly the best route, as you must determine the best route based on what is a safe road/street to be riding your bicycle on!

Within four to six months, possibly sooner, even with short daily outdoor rides of at least five miles and you'll be on way to riding 22 to 25 miles without any struggle at all. You gotta get back in the groove and learn to use your gears. The object should be to make the gearing do the work..............NO NEED TO INITIALLY TRAIN AS IF YOU WERE GONNA COMPETE IN A TRIATHLON NEXT MONTH. Racing as fast as possible IS NOT YOUR GOAL!!! Just Ride for enjoyment and listen to your body, and don't overdo it. After a few months, you'll be back in business, such that if you wish to then Speed things UP, then do as you wish. Hey, maybe by late 2021 if the vaccine allows for Triathlon competititions to happen again, and you are also able to seriously swim and also train not only by doing laps in a heated Olympic sized pool in wintertime, but in fresh water lake & river with wind waves and current when Memorial Day, 1st of June rolls around. You gotta train in real water that approximates both the water temp and expected water conditions that you may encounter during the Tri. Running is the easiest part but you gotta have juice left in the Duracells after getting off the bike to do the Energizer bunny run to the finish. The TRANSITION times cannot be overlooked as transitioning from the SWIM to the BIKE, and then the Bike to the RUN is where huge amount of vital race time is Lost or Won. Cyclists generally SUCK as first time Tri-Athlon Competitors BECAUSE THEY THINK THEY WILL BE SIGNIFICANTLY BETTER ON THE BIKE PORTION than other competitors Which Is Just NOT TRUE. Riding a bicycle fast is the EASIEST LEARNED of the three needed skills. Swimmers generally kick cyclists' asses, as do Marathon runners who are also decent swimmers.
Who really cares about 50 miles on a bicycle in one ride? Sheesh, go down to FLORIDA and you can likely train in two weeks from never having ridden to the ability to ride 50 miles on a bicycle in one ride because everything is billiard table flat.
An ordinary triathlon of say a 1 mile swim, 22 mile bike ride, and 10k run is far more fun than just a 50 mile bike ride.
Tri competitors are generally far better athletes than cyclists. Most tri competitors are also serious cyclists, serious marathon runners, serious swimmers, and serious highly ranked amateur tennis players. It is a heck of a lot of fun, and tri competitors are encouraging to novice newcomers, as it is known that all the podium winners in the various age classifications are decent overall and surprisingly not all of the winners are riding expensive bikes at the ordinary triathlons. 70.3 Half IRONMAN competitors generally have much more expensive sophisticated equipment for their 56 mile bicycle portion.

Have fun riding your bike and getting exercise. If you find it fun and enjoy it more, you'll likely continue to make time for doing it.
You aren't doing the Tour de France in July 2021 , and you aren't doing IRONMAN Hawaii in 2021, so why the heck worry, as if you're trying to qualify for the US OLYMPIC TEAM or something. GOALS ARE GREAT, BUT BE REALISTIC AND HAVE FUN RIDING AND YOU'LL KEEP ON RIDING SUCH THAT YOU'LL GET STRONG ENOUGH TO DO 50 miles in one day WITH EASE. You don't need to do the 50 miles at LANCE'S pace. Remember that Lance had world-grade pharmaceuticals assisting him and he was also a young superb world class athlete at that time.