This next sentence may sound obvious, and I already posted something similar earlier in this thread, but unfortunately it seems to be needed again: If the OP was paying rent, then the rent will be looked at as rent.Obviously the court will look at all of the evidence, if the $10,000 was in one large chunk, or can be proven to be spent on improvements, then perhaps it will be looked on as a loan. however, if this person was tossing in a few hundred bucks every so often, you can bet it will be looked at as rent. Horse hockey on the lease thing. There are many many tenants throughout the universe who do not have written leases and yet pay rent. Not alot of smart tenants, (or landlords), but there are many.
In other words, that's a factual issue. However, the OP never suggested that there was any dispute as to whether the $10k was for rent or home improvement; it was for home improvement. Nor did the OP ever suggest that the $10k home improvement money was in lieu of rent (i.e. if you pay for this repair, you don't have to pay rent).