If he is indeed serious about this project, he will ask somebody to join him on developing this project.
Running solo especially he can't fulfil the role of a developer would just be a failure.
These days, crypto users are now smart with their investments.
They will not spend their investments without the basics of a project like website or at least MVP.
So I can say, you can't safely or successfully launch a private without any reference that your projects exists.
I've created a thread for this purpose here
https://bitcointalk.org/index.php?topic=5245078.msg54340717#msg54340717 .
I can tell you one thing that this may help you a lot with your problem, you must read how single developer that created byteball platform and it was also launching its own personal ico
https://en.bitcoinwiki.org/wiki/ByteballIt may help you a lot to launch a privatesale without a team and you must know that product is everything in this case.
Byteball may have take to the developer a lot of time (at least 6 months) and he is probably a senior in blockchain and also had implicitly some potential investors.