Let's start by hand-waving all the physics problems like friction, momentum, etc. We can use a made-up term that is totally original and not inspired by other fictional speedsters.
VelocityStrength or something along those lines.
So assuming that VS takes care of all the (billions) little problems that come from such a speedster, like breaking keyboards, running out of air and completely destroying everything around from extreme air pressure changes, now our speedster, let's call him Barney Warren, has several things to take care of.
Since the mechanics of this speedster as a baby are ridiculous, and you didn't specify if the power is natural or obtained later, I will only take into account adult life. I will aslo assume that this speedster ages in real time, and not in subjective time, because otherwise they'd die of old age within hours.
Time factor: 1 subjective hour = 86400 real hours
Until Barney succeeds at communication, nobody knows he exists. Unless he is willing to stand still for days (one day = one second), nobody will ever see him. Any sound he makes would be far too high-pitched to be heard by humans or animals, and any physical contact would either instantly destroy the target, or be protected by VS and do basically nothing.
The speedster then needs to change something in the environment to communicate. Writing messages is obvious, whether it is on paper, in the sand, by email, etc.
But if he wants the communication to be two-sided, he needs to be incredibly patient. What is the most likely to happen, provided this speedster is a good guy, is that he will steal a lot, but people will like it. If he is a villain, we'd all be conquered or killed within a day.
Just like everyone else, he has needs. As for food and water, his needs are probably roughyl equal to 86400 people for the same timespan. That's a LOT of ressources, and he has to obtain them without people's consent, because he'd die of hunger before anyone could say yes (at least until he establishes a decent rotation, like ask 100 000 people and pay them, then come back to the first to collect after he gave consent, etc)
I think the most logical course of action is to go do jobs hat are time sensitive, and steal the pay (while leaving a written explanation). Barney finds some place where people are doing physical work. He then uses his near-infinite time to figure out how much the owners are paying, calculates the total (hourly pay * number of workers * time to completion), then does the entire thing instantly (from our perspective) and steals this precise amount of money. While technically illegal, I'm pretty sure paying the same amount to get the work done instantly instead of over months would leave many owners very happy.
Then he can "buy" things the same way. Steal what you need, figure out the price, leave the correct aount of money with a post-it on it explaining exactly what you did. Some people literally do the same in gas stations if the clerk is busy and they are in a hurry, but in seconds instead of milliseconds.
Considering the incredibly rate at which Barney would do those operations, pretty much everyone would be aware of him instantly. After a very short time, some people would start making official offers to him (X amount of money/food/etc if you come do this for me), which would take into account the incredibly fast work, and would probably pay more.
Not everyone would like it. Barney would be "stealing" many more jobs than any illegal alien ever did. But I assume that by catching bad guys or saving lives every now and then, Barney could keep a relatively nice reputation and be liked overall.
As for personal connexions, it's just impossible. Long distance relationships have a much lower rate of success because distance, and delay in communications, are a huge burden on relationships. Imagine a guy who would have to wait months at a time even for the simplest answer to a question?
I'm sorry to say, Barney will never be friends with Risco and Katelyn.
As for my personal opinion, while he might not turn into a total villain, he will definitely not stay that nice for long. Nobody can stop, threaten or even lecture him. Sooner or later, he will start to work less and/or take more, and at some point will straight up just take. Nobody is holding him accountable anyway, and physical work will get boring/tiring extremely fast, especially alone. Keep in mind that while the work is done within minutes, Barney had to do maybe months or years of work, on what probably looks like a normal person's Schedule (8-12hours a day), without any help, teamwork or person bringing refrreshments. And as opposed to us, he can't look forward to being done after a quick 45 years.