Which is better for a SOLO 1 man developer? UE4 or UT5?

I have an idea, what if I spend some money on UE4 marketplace?

Say I spend about $200 US when there are sales 50% off etc? this should give me a great headstart right?

If I buy a top graveyard or top down dungeon etc, would I be bale to build upon it? does it come in the format necessary to be opened in Blender? where I could duplicate already made buildings and houses etc and modify them etc?