Google drive is a good option as the artist can give you a link to a asset or a folder for the project, it also gives a lot of space and works with your Gmail account. This means the artist will only have to provide you with his email address and you can pay them for their work with paypal.
Notes:
If you pay the artist per asset instead of the hour, they will not want to upload 3D models if you don't pay for them, this can make it hard on you to review the model as you have to do it by image or video.
I recommend using a imbedded option to view the 3D model, the artist should also be able to provide it as a .exe.
Provide your artist with images of both the type of work you want and quality.
Don't expect top work for low pay, as artist we have a amount we are willing to spend a day working for, lower prices will get you rushed work.
Check the license agreement with the artist.
Confirm what you are paying for, the work or the model. Different laws apply to the different work that is done.
Ask for the master final files, because your artist wont backup the files forever, if you need changes you will have to give them the file to work with.
Remember that you can always scale assets yourself, it's easy, you don't have to pay the artist to resize.
Last: Less than half the projects ever made see a release date; to make some money you can sell all you own, if you and the artist agreed.