@Ella6386.Of course you can negotiate. Isnt it your place?
In addition to the great advice here, please investigate your legal obligations as a potential landlord of a longer term rental. I know there was a six month stay that appeared to go well for you but you really need to be sure as sometimes guests will take advantage.
For example, in my state any rental subject to a lease must set out in an agreement who pays the utilities. Normally here a tenant pays 100% of electricity (so account goes in their name and you arent left paying their bill) and water (usage only but not daily charges for water and sewerage services, thats paid by landlord).
Insurance coverage may be easier or harder to obtain. Factor all these costs in first, work out fair wear and tear, compare your offer to local furnished long term rentals then set your offer. Be the price maker, not the price taker.