The producer's home studio
The first rule of home studios is that they are not compulsory!
Many musicians have home studios because a good home studio can be much less expensive to operate than to hire even the cheapest and crustiest commercial studio on a regular basis.
But if you are working at the highest level of music, then you will have the budget to work in a top studio, and if you are successful you will be doing so regularly.
If you work with sequenced music however then you will obviously have your own keyboards and sampler, and a sequencer is an inevitable extra purchase, so effectively you have acquired a studio without really intending to do so.
The question now would be how much of this equipment do you want to transport to a commercial studio once you have sequenced your basic tracks?
Bear in mind that taking your whole setup apart and re-erecting it somewhere else isn't a whole load of fun. In this field of music it would be wise to find a well set up studio which you could use, which may be tied to a label and not operating as a commercial studio in the normal sense of the word, and choose equipment similar to theirs.
If you have the same sampler and sequencer, you might find that all you need to take with you are a few floppy disks and maybe your source material for loops. The synths might be different models, but it shouldn't be too much trouble to find sounds that fit what you have in mind.
Since you have the basics of a recording studio at home already then a worthwhile next step could be to record vocals there too. You might just be thinking of trying out a few ideas, or your singer might suddenly get the urge to record and it would be wise not to waste their energy and enthusiasm.
To record vocals you need a quiet, dry acoustic, a good microphone (such as that perennial favourite the Neumann U87), and a digital multitrack to which you can synchronise your sequencer. If your mixing console isn't really up to the job then you should buy a rack mounting mic preamplifier.
The mic and preamp will cost a bit, but if you are recording vocals at home you shouldn't skimp on cheap equipment. Your equipment must be exactly as good as the equipment in a top studio, even if you don't have as much of it.
If non-sequenced bands are your speciality, then there isn't much point in having a home studio. If it was good enough, then it would have cost so much you would have to open it up for hire to make it pay, and I think you probably want to be a producer rather than a studio manager!
This doesn't mean that you can't do some work at home. You may have a digital multitrack and a small mixing console which you can use to compile parts of several vocal takes into one good one.
This can be time consuming, and you can probably do it better by yourself in your own surroundings. You may also want to have a computer and sequencer for the odd bit of sequencing that needs to be done, or to prepare click tracks in advance of the recording session.
There are no rules, just consider what is practical and cost effective to do at home, and remember never to lower your standards and do something at home which you could have done better in a proper studio.