We don't limit the number of challenges you can purchase, and you can even take part in multiple challenges in parallel. However, When it comes to active accounts being run in parallel, each user will be able to have a combined starting equity of a maximum of $200,000. This means that, while you can not exceed a total of 8 challenges running at once, you will be able to purchase an infinite amount of challenges provided they are within the $200k combined starting equity limit.
For Example:
This means that you can have a total of eight $25K challenges running at the same time. Similarly, you can have a total of four $50k accounts. You can also mix challenges and for example have two $25k accounts, one $50k account, and one $100k accounts simultaneously, however, you will not be able to purchase five $25k accounts and three $50k accounts.
Please also note that, if the $200k limit is reached, you will be able to purchase more challenges once the ones you have purchased are completed.
To summarize, you can buy accounts until you reach a maximum of $200k total starting equity of all accounts combined. That said, you can scale up your capital as far as $5 million on all accounts by staying profitable.