There is no limit as such on custom views per user but the more the number of views the more server space is occupied.
It is better to limit it with needed custom views to save server space and make the server run at optimal speed.
Hope it helps.
Is there a limitation on number : no limitation as each is a separate view/workbook by itself.
Will it have any issue ?
It depends, if it impact or not on your server/infra - depend on how you want to build and how you want to use it.
Few scenario from my point of view-
If you have live connection and fairly simple use cases - Server space should not be a constraint.
If you have live connection but you want to integrate your tableau metadata with some enterprise information like say (HR Reporting hierarchy etc). you may have slow experience but might not have space issue.
If you want to built several custom views using lot of metadata information and duplicate the tableau data model one or other way and build many extracts without any filters ... you might run into space issue .
if depends how you want to use or re-use the meta data model to know how it will impact on your environment and end users.
Consider and minimize duplicate data model as much possible , if you have plan to build several similar custom viewes from similar data model.