How to check up on your potential tenant:
Check out the tenant on Google and Social Media
Check the tenant's profiles on Facebook and LinkedIn, for example, and search for them on Google. If there are discrepancies in what they have said, there might be a reason behind it.
Is the tenant a little too eager?
If a potential tenant can "pay today and move in tomorrow", it's a good idea to find out why. Has the tenant been evicted from the previous tenancy or what is the reason?
Have a dialogue with previous landlord
If the tenant has rented before, you can ask to speak to the previous landlord.
Is the tenant a business owner?
If the tenant has a business, you can check solvency etc. in various places online. If they have a history of 15 bankruptcies, they are more likely to have problems with rent payments.