Paying rent in advance

[Izac Sheforgen]

Hello! I am renting out one side of my duplex and received an application today from two former military officers. I let them know ahead of time that I do background and credit checks on all my tenants. In response, they reached out ahead of time and made me aware of a credit situation. Due to Covid they had a Tennant themselves who failed to pay rent which caused them to fall behind in their mortgage payments and ultimately had a large impact on their credit. 

As insurance to prove they were financially secure and responsible, they offered to pay 4 months of rent in advanced. Would it be wise to accept this offer if everything else checks off in their applications? I know I’ve heard this can be a red flag, but I’m wondering why it would be a problem? Any suggestions would be greatly appreciated!