Just a thought: it would likely be cheaper to just add an appropriate 50-amp outdoor breaker box to the outside attached to the load center where power comes to your home, then run the circuit from there to your EVSE. If you must bury the circuit, it will be far more expensive for the digging than if you could run the conduit attached to the outside of the house or through it (attic?, basement?) somehow. As always, local codes will define or negate this option.
Suggest you try to avoid the cost and long labor time to replace and re-wire an outside load center, or inside breaker box. Add-on service is usually much cheaper, dedicates the EVSE to its own supply, and doesn't reduce your available power for the rest of the house.
Last item is the distance. The NEC and local codes set wire size requirements, and the size is determined by the carrying amperage of the circuit and the distance of the run. Wire of the sizes needed to safely carry 50 amps with minimal voltage loss and code compliance can get expensive quickly, even more so if it has to be in conduit, or is the type of wire than can be buried. A local licensed electrician should be completely aware of (a) appropriate wire sizes for your application, (b) code installation requirements, (c) permit and inspection requirements, and (d) good practices.
Final suggestion: have a circuit breaker installed upstream of your EVSE but close to it so that you can easily shut all power to the unit for installation, troubleshooting, replacement, etc., and not have to trek back and forth to the load center.
