Doing it yourself at high quality is pretty snappy. You just need about two to three months to learn how, and higher understanding of trigonometry, materials, and armatures.
There’s plenty of free entry stuff you can use to copy/simplify the tedious bits like weight paint onto your models.
Basically even exporting a paragong character and transferring weights by distance from it will do, but using a make human generated base will probably do it better.
And make human had compatibility with the ue4 rig 10 versions and a year ago, so I have no idea what you are on about. Surely They didn’t remove a feature that existed.
I hate to break it to you, but “once I make reliable income with my game” = never.
Don’t count on it, games don’t offer steady income to begin with, let alone for an indy dev/studio.
Animations:
Ureal marketplace animations- the free ones - are trash. They rely on skeletal retargeting and often have bad animation tracks for several bones. So saying “my custom character doesn’t work with retargeting to these animations” doesn’t mean jack. You can make it work with the proper skeletal settings just like the mannequin works with it.
Make your own / learn how.
That’s an important skill to have since you will always be making new ones for stupid little actions as you make a game (opening doors, driving cars, picking up flowers, etc) that you just won’t find form the marketplace.
once you know how, it takes about 2 hours to make a good animation from nothing at all.
Also, you can now make them in-engine with Control Rig. Never used it so not sure how good that actually is. I prefer using blender so I have copies and backups.
The theory is the same. The difference is that the tracks made in unreal will always look the same as you made them. Those you import may change slightly depending on settings.
Last thing.
As with Everything, you have evolving tools and changes to the engine.
Hair grooms for example. Or the now supported morph target adaptation to joint bending. Chaos physics, including cloth. And a bunch more things that will always be in Flux, so unless you start getting your hands dirty with some character guts yourself you’ll never actually manage it.
even expensive marketplace assets can be obsolete in less than a minute with all the changes.
If you put the work in, high definition final results at home are completely possible.
they probably won’t be as good as the unreal professional captures seen here Digital Humans | Unreal Engine Documentation
unless you do have several $10,000 to dump into gear for captures. But the methods listed On that link, are a very viable starting place to understand what goes where.
As far as “do it at home” I recommend a good camera and MeshRoom for getting a photogrammetry start - not of the model mind you, but of the skin textures. Skins are hard.
You can pop the good model with the good UVs into mushroom and have its photogrammetry algorhitms pop out the skin/roughness/normal for you. Compared to painting it by hand when making realistic stuff at home its a godsend.