You can certainly tune a bass guitar in fifths if you like, there is even a club for that. The fifths tuning is actually a very nice choice for a bass guitar and some DB players also use it. To the best of my knowledge it was the DB musician Red Mitchell who inspired some of us to try fifths in fact. If you want to copy existing pop/rock/jazz bass lines then fourths has the advantage that they were all written around what is easy to do in that tuning. Most of the time you can do them in fifths too, but if all BG players had tuned in fifths from the beginning then the classic bass lines would have been written differently because some of them are challenging in fifths. If you want to try to play the Bach Cello Suites on a BG then fifths is a good choice. It will also encourage you to be different and perhaps, if you are good enough, stand out from all the other bass players. These are not bad things. I have to buy custom string sets but not being able to play someone else's bass has never been an issue for me. If you want to keep that ability but tune in fifths then just carry around a set of strings for the fifths tuning. You can convert any bass in the time it takes to re-string it and no harm will be done to the bass.
If you tune in fifths then you will have no learning curve to climb when it comes to playing from music because all the notes will be right where you expect them to be. Except that they aren't. They are too far apart!! So there will be some learning either way. If you go with a short scale bass then its 30 inch scale will be closer to the 27 inch cello scale you are familiar with. Maybe that is an advantage but maybe it would be better to go with the traditional 34 inch bass scale because being close to what you expect but not quite might be harder to adapt to than a larger scale difference would be. I have no personal experience with this and mine might be different from yours anyway. One down side to the shorter scale is that if you choose to tune CGDA but an octave below a cello then that low C is a bit low for the 30 inch scale. I'm happy with it on my one short scale bass but certainly not everyone here on TB would be. You can probably find some nice used basses for $75 if you look around and you can get some nice new ones for $200 to $500. No need to spend more than that really.
If you decide to tune in fourths the way nearly everyone else does then you can undoubtedly learn to deal with that. People play a lot of different guitar-like instruments with different tunings without issues and you would not be the first to move back and fourth between the BG and a violin family instrument either. One of the other people who inspired me to try the fifths tuning, Dennis Masuzzo, tunes his DB in fifths but has kept his BG in fourths! Or at least he did the last time we chatted. I switched from fourths to fifths and if you want to go with fourths you should keep in mind that the two actually have three strings, not just one, in common. Both tunings have A, D, and G strings and even though those strings are upside down from one another between the two tunings it actually helps quite a bit that they are common between the two tunings. Red Mitchell retooled his thinking from fourths to fifths over the course of a one week long vacation. I'm no Red Mitchell, nowhere close, but it only took me two weeks.
So whichever way you decide to go it is a very doable transition and you should quickly become comfortable switching back and forth between the two instruments. Welcome aboard and enjoy the ride!
If you tune in fifths then you will have no learning curve to climb when it comes to playing from music because all the notes will be right where you expect them to be. Except that they aren't. They are too far apart!! So there will be some learning either way. If you go with a short scale bass then its 30 inch scale will be closer to the 27 inch cello scale you are familiar with. Maybe that is an advantage but maybe it would be better to go with the traditional 34 inch bass scale because being close to what you expect but not quite might be harder to adapt to than a larger scale difference would be. I have no personal experience with this and mine might be different from yours anyway. One down side to the shorter scale is that if you choose to tune CGDA but an octave below a cello then that low C is a bit low for the 30 inch scale. I'm happy with it on my one short scale bass but certainly not everyone here on TB would be. You can probably find some nice used basses for $75 if you look around and you can get some nice new ones for $200 to $500. No need to spend more than that really.
If you decide to tune in fourths the way nearly everyone else does then you can undoubtedly learn to deal with that. People play a lot of different guitar-like instruments with different tunings without issues and you would not be the first to move back and fourth between the BG and a violin family instrument either. One of the other people who inspired me to try the fifths tuning, Dennis Masuzzo, tunes his DB in fifths but has kept his BG in fourths! Or at least he did the last time we chatted. I switched from fourths to fifths and if you want to go with fourths you should keep in mind that the two actually have three strings, not just one, in common. Both tunings have A, D, and G strings and even though those strings are upside down from one another between the two tunings it actually helps quite a bit that they are common between the two tunings. Red Mitchell retooled his thinking from fourths to fifths over the course of a one week long vacation. I'm no Red Mitchell, nowhere close, but it only took me two weeks.
So whichever way you decide to go it is a very doable transition and you should quickly become comfortable switching back and forth between the two instruments. Welcome aboard and enjoy the ride!