If we are talking here about a base, well the first thing you need is me. Dr. K Kerbal. The specialist in planetary bases.
If you are building in the clouds, you need to limit your parts into a minimum of about 150 and no part can be heavier than 5 tons. If any of the parts are over that limit, then your toast. On the venus surface. You will need an emergency engine incase that use becomes to heavy for the clouds to handle so need some fuel in spare. You will need a transfer stage with about 1250 metres of delta-V to get into orbit and transfer your crew back to Kerbin. The thing with the transfer stage is that it has to have enough TWR so you don't have to start your escape burn too early. If you use nuclear engines, ( Witch would be useless on the surface on Venus because it has an atmosphere) you will need a lot of them depending on the height of your orbit. The higher your orbit, the less TWR you will need. This is because, if you start your burn 5 minutes before the required time, you will not notice ( Unless if you have KER ) that you eventually suicide your orbit and before you know it, it's too late.
Also. Be careful of heat. The surface of Venus in the real world aka. not in ksp is about 400 degrees celsius. So if you had ablation, it would probably be gone in about 10 minutes. And there is no little cross next to the ablation bar. So be careful. Also if you have a space station around venus, try and get it into a really low orbit, because then when your transfer rocket leaves the base, it will be a very quick ride to the space station if you are going there.
Oh my goodness. My fingers are getting tired. I will be back on this forum in a bit so don't delete it. see ya later.
Dr. K Kerbal