is there any limit for parallel execution? if yes, how to find out the maximum limit?

I am creating a script which create a string of scripts concatenated by '&' and uses eval to execute them all together. Something like this:

scriptBuilder="ksh -x script1.sh & ksh -x script2.sh & ksh -x script3.sh";
eval $scriptBuilder;

Just wanna make sure what is the max limit for parallel execution on the server. Any help would be appreciated.