There is a third alternative (not stowing away ... okay a fourth alternative) a group could own a spacecraft like a launch. A Cepheus Engine style twenty ton launch runs about 4-6 megacredits. If you're paying attention that's a monthly mortgage and expenses of 14,000 to 21,000 credits per month new, far cry from the mortgage for even a Courier. Crew are also small so your payroll is more manageable. If you aren't making a jump you don't need to blow money on refined fuel. Leaded will do.
But you can't make jumps. Why would you want to saddle yourself with a shuttle?
First of all in some settings you can make jumps using wormholes, star gates or what have you. You you may just have to pay for it. Since it costs 1000 cr. to ship one ton planet to planet, a launch would cost 20,0000 cr. and be at some discount considering it is jump point to jump point or even free if you use natural wormholes.
A launch has 10.9 tons for cargo at most. The ten grand for shipping won't cover the mortgage or expenses unless you have a rush job and are being comped for stargate use and are charging more than that 1 cr. per kilogram. This is possible for express jobs or flights into dangerous situations. Doubled fees might not be out of line which would cover expenses and pocket money.
It is possible to engage in speculative trade. You can make money but you can also lose it and get your ship repossessed. You really need an FTL drive to properly skip on the banks. They have a long reach and never forget.
You could also set up in a system with a lot of settlements on different planets. A gas giant with several settled mooons could provide trade and travel opportunities for an entire campaign. For that matter a launch could provide hypersonic transport between points on a single world. If that planet is TL7 or less you are likely to be the fastest thing around.
If trade seems a little dodgy there are other business models. Search and rescue, hunting parties, research expeditions might want a gig hanging around but not want to rent a starship to hang in orbit for weeks. In this case the gig would ride in the cargo bay or in a berth on a rented merchant to its destination to perform its services. This would be ideal for a cash strapped organization. Say a university sends an expedition to investigate anomalies on the moons of a gas giant. They need transportation among the moons for a couple of months. They only need a starship to get there and back. A starship has a much larger mortgage than a launch (at least 5-10 times the cost to rent). They instead hire and ship a gig with their expedition to ferry several parties among the moons to look for shiny stuff.
Similarly a low tech world with several colonies and outposts in system might hire a launch for routine cargo runs and become a base for adventures in a campaign.
There are many options for fitting a gig for voyages of several weeks. This might be necessary when a remote outpost needs a good or service from the mainworld but a merchant ship doesn't want to perform a micro jump or truck it out via STL and lose time spent in more profitable trading. If a planet is occluded by the jump shadow of it's primary it could also require additional jumps or a long trek that a gig might perform more economically.
Refits include permanently changing cargo space over to staterooms. Since most launches only have a ten ton cargo capacity a cabin for two will almost halve this. Small crafts typically use accommodations similar to cube hotels. Passengers and crew often make do with living areas similar to the ancient NASA expeditions on short trips.
(The Tokyo Capsule Inn is a good example of compact but cozy accommodations.)
In settings with more dependable forms of cold sleep, low berths are favored with automatic systems waking the crew when their expertise is needed. Other enterprising individuals have bought and installed stowaway style crates (after knocking a couple of windows in them).
(An example of the low berth section of a starship ... hey wait a minute!)
A mercenary unit might be forced to use a small craft transported by a larger vessel for several reasons. Security is one. Some merchant vessels do not care to have a number of proficient killers onboard and a stroll from vital areas of their ship and some commanders are wary of unit members spilling plans to just anyone. Some captains will also have a problem transporting heavy weapons and explosives in their hold. For the security and safety of both ships it's sometimes better to transport a whole small craft.with its contents and occupants locked behind a hatch (that can be blown at a moment's warning.)
The mercenary team might also require certain features on an assault or insertion shuttle. Instead of hiring one on, they bring their own.
This might be the common transportation method for groups transporting particularly valuable cargo. Why trust a merchant's security systems and crew when you can trust your own. The transporting ship also provides an early warning of scurrilous activities (when their crew starts getting shot grab your guns. In the event of a pirate attack you have an extra ship to run to. The list goes on.
Me, paranoid? Maybe but being paranoid doesn't mean you don't have real enemies. it just means they're a sort of external validation!