Well if you advertised that it's street parking and verbally agreed, then you may probably tow his car for "illegally" parking his car in the drive way.
Do you have other house-mate tenant that can back up the oral agreement regarding the Parking situation? Like is everyone aware and agree what the Parking situation is?
Also, the laws are bit different when it's owner occupied/shared housing.... but you should check your state and local housing law. Sometimes it's more landlord friendly when the landlord lives with the tenant. Even better, talk to an attorney. The first consultation is usually free and they can guide you on your next step if you plan to take it to the court. It gives you an idea what to do next.
And for future lease agreements and contract, even if it's a small matter... write it down and have them sign the agreements along with the lease term.
- parking
-responsibility/roles: cleaning/ trash/ common areas / parties / pets / guest over / noise level / recreational drugs / etc
There are so many things you need it written down, especially in shared housing with a tenant. It may be fine initially but the problem may come up in the future more frequently and hinder living situation for the landlord and other tenants living in the same house. You never know so it's better to be prepared than not to be prepared. Having rules and enforcing it is also good.
For example, I did shared housing during my college years. I would have my house mate tenants let me know in advance of minimum 1 week if you have guests over and require that they let everyone else in the house know as well. Also it has to be only on Friday and Saturday night on non-working/school night so people can go to sleep soundly. I eventually had to put a cap on number of guests a tenant can bring for future lease term agreements because one of the tenant thought if guests are okay...it's totally okay to bring 20 ppl over... NO. That was not okay for everyone else. The tenant's small "kickback" literally became a house party. I literally said I'm calling the cops if they are not gone in 1 hour. Needless to say, things became ugly and the tenant moved out. Never had a problem before until this tenant moved in and made it a problem that required to be written in the contract.
Have you ever wondered why some common sense laws/ rules are even necessary? It's because of THAT one person that made it into a law.
In addition, if they have a guest over, usually bf/gf sleeps over. I had one tenant that had a bf over for 3 weeks. Extra person means eating up utility costs for shares utility and rent space for the landlord. So I would do weekly pro-rated rent with prior approval of long term guests with maximum stay of 2 weeks. And I would put single occupancy only per room in the contract as well... and then add an admendum of house rules.
since verbal/oral contract is not really held high in court... if you can't sign the contract write away then use technology such as text message or emails or even voicemails.
***Oh and save your ad posting regarding the parking on the street in case if your tenant or you go to the legal route.