Is there a minimum? for Ether or btc?
No,
You can invest as much as you want.
Have you done any due diligence? People doesn't do anything!
Here is mine:
$5.5 trillion market size.
Competitor 1s capital $92b with 87m reward members ~ $1057 member value, $4.2b profit.
Competitor 2s capital $80b with 70m reward members ~ $1171 member value, $5.3b profit.
by 2022:
Litra apps member value on average $ 1114 + EHRs Magic.
EHRs Magic worth $500 - $1000 per member.
Litras Member value = $1614 - $2114.
300 million Litras members.
$1614 - $2114 x 300m = ~ $484,200 Billion - ~ $634,200 Billion Market value.