Weapons and cash from the US are not loans. There was a lend lease act passed, but it was nothing. It literally only takes up half a page, you can read it yourself, there's literally nothing there. It was just a sign of support, meant to take the headlines away from whatever shenanigans Russia was doing at the time. Actual weapons are sent using the presidential drawdown, which doesn't have to be repaid. Some other countries like Germany have lent cash, but on pretty generous terms, if you read the agreements, you might hesitate to call them loans at all. Lets not forget that this is not coming out of nowhere, Ukraine is asking for support. Its not being forced on them. During existential war, a lot of things fall down the list of priorities, like balancing the budget for instance.
When it comes to rebuilding Ukraine, I am pretty sure, most of that money is going to come from the west. Even if Ukraine regains all its territory, there's about 0 chance Russia will pay reparations, except for perhaps, what assets were frozen.
Russia WILL end up paying in one way or another. Since Russia has no large-scale digital foundries (it has a plan to build a 28nm facility by 2030), it's going to be almost entirely reliant on China. We live in an age where the IC is essential to every developed nation.
Unwisely, basing a war based on the fact that a nation was previously part of The Russian Empire also plays right into the hands of China whose stated aims include rectifying 'a century of unequal treaties' (as Mao termed it). Well, Manchuria was part of the Chinese empire until 1858 BUT was never part of the classical Russian Empire.
I might add that China is facing a chronic water shortage and just within Manchuria is lake Baikal, the largest freshwater lake (by volume) on the planet. China intended to build a pipeline to solve it's truly vast water shortage. They bought land around the lake and a lot of the land connecting the lake to China... then Putin blocked development in 2017. He recognized that it represented the simplest way to slow the development of China.
I'm not sure if China considers it's water shortage as an existential threat but it's certainly an increasing problem with between 80% and 90% of it's groundwater now considered unfit for drinking.
I SUSPECT that is why China has carefully NO picked a side in the Ukraine conflict. From their perspective, the war is serving to destabilize Russia, expose the weakness of it's military and use up much of Russia's military strength. It doesn't matter to them who wins just as long as it weakens Russia sufficiently to at the very least give them access to the water.
Meanwhile, Russia having made itself a pariah state ensures that NOBODY is about to lend aid if China does end up having to use force. I'm sure China would much rather come to a deal, but in spite of the surface-level civility between Russia and China, that pipeline is vital to China and it's ONLY benefit to Russia is in it's strategic use of limiting Chinese development.
I think most people aren't aware of the above situation because it barely made the news (in Europe and America) in 2017 but it's created a huge divide.
I should add that Russia is also seeing a population crash. The population is aging (current birth-rate is 1.5 children per woman) and those with ability are leaving because conducting business in a dictatorship where corruption is the norm rather than the exception isn't very attractive.